Chemistry: Structure of Matter and the Periodic Table

What is an isotope?

An element with the same number of protons with different number of neutrons.

What is spectroscopy?

Deals with the interaction of matter with light.

Electron Affinity

Defined as the energy required to add an electron to the ground state, in the gas phase. So we're going to start with a certain element in the periodic table and add an electron to it so it forms an anion. It's going to have a negative charge instead of a positive charge. It's not exactly the same as ionization energy, but it's related or similar to ionization energy. Trend: increase in electron affinity as I go across, and decrease as I go down. But there are some exceptions.

What is the name for N2O?

Dinitrogen Monoxide

Formula for energy (E)

E = hv = hc/λ energy = Plank's constant * frequency (symbolized with nu) = (Plank's constant*speed of light)/wavelength of light

Who is JJ Thomson

He did the first experiment that lead to our current understanding of atomic theory. He used the cathode ray tube to produce cathode rays. He found out that particles have to have a mass and a charge. He really wanted to figure out the mass of the electron and the charge of the electron. He never got the individual numbers for the mass of the electron, but he got the ratio of the mass to the charge.

Accuracy

how close experimental values are to a true or accepted value

Precision

how close experimental values are to each other (consistency)

What are spectator ions?

identity is irrelevant, however they are necessary for charge neutrality

Beta plus decay

positron emission - loss of a positron ⁰₁e A positron has the same mass as an electron (0 or very small number), but has a charge of +1 instead of -1. A positron is the antiparticle of an electron ²²₁₁Na→⁰₁e+²²₁₀Ne

What are the 2 types of agents?

reducing agent - causes a reduction - metals make good reducing agents bc they like to lose electrons oxidizing agent - causes an oxidation - nonmetals make the best oxidizing agents bc they like to gain electrons

Main-group elements on periodic table

s block - alkali metals and alkali earth metals. All of the s block have valence electrons in the s orbitals. p block - metals, metalloids, and nonmetals. All the p block have valence electrons in the p orbitals.

Predict by what mode(s) of spontaneous radioactive decay the unstable isotope (6)(2)He might proceed.

⁶₂He 4 neutrons, 2 protons You would want to increase the number of protons. beta emission to ⁶₃Li

Transition metals/elements

Found in the middle of the periodic table. Have d and f orbitals in them, so the d block is the transition metals and the f block, which is the little strip on the bottom, is all of the rare earth metals. These are considered inner shell electrons bc the energy levels are actually lower than the principal values. In other words, if you kind of scan the periodic table and go from left to right, you might have electrons in the 4s energy level and then it goes down one level to the 3d and then it goes back up to the 4p.

Electron Capture (a type of beta decay)

Gain of an electron Ex. ⁷³₃₃As+⁰-₁e→⁷³₃₂Ge Net conversion of a proton into a neutron [(A-Z)/Z too low]

Atomic radius

Generally atomic radius decreased across a period and increases down a group. This is a periodic trend. Basically refers to how big the atom is. Trends for atomic radius: As you go horizontally across, the time of radius decreases meaning the atoms get a little bit smaller, and as you go down vertically in a group, the atomic radius actually increases- they get bigger.

What is the group number on a periodic table?

Group number tells me how many electrons reside in that energy level. For example, if I have a group number of one there's one valence electron or one electron in the outermost energy level. Group numbers go vertical.

Who is Joseph Balmer?

He came up with an equation that was able to predict the positions of the lines for hydrogen. Late 1800s

Who's Mendeleev?

He created a version of the periodic table.

Radioactive Decay

In order to achieve stability, radioactive nuclei will typically try to change their (A-Z)/Z ratio so they can fall in the band of stability. (alpha and beta decays) It is also possible to become more stable yet keep the mass of the nucleus the same. (also called gamma decay) Other possibilities are fission (splitting of a heavy nuclide into smaller nuclides) and fusion (joining lighter nuclides into a heavier nuclide)

What will happen to groups (vertical) on periodic table as you get more and more energy levels?

Increase in the number of principal energy levels. Which makes sense, because that means that there's a bigger distance away that the electrons are in the valence from the center, from the nucleus.

What is the ionic and net ionic equations of: HCl (aq) + NaOH (aq) → NaCl (aq) + H₂0 (l)

Ionic: H⁺(aq) + Cl⁻(aq) + Na⁺(aq) + OH⁻(aq) → Na⁺(aq) + Cl⁻(aq) + H₂0(l) Net Ionic: H⁺(aq) + OH⁻(aq) → H₂0(l)

What is the purpose of ionization energy and electron affinity?

It is the energy required to, respectively, remove an electron from ground state and add it to ground state.

Based on their positions in the periodic table, list the following atoms in order of increasing radius: Mg, Ca, Rb, Cs.

Mg < Ca < Rb < Cs

What are the prefix names for 1-10?

Mono, Di, Tri, Tetra, Penta, Hexa, Hepta, Octa, Nona, Deca

Whats the chemical compound name for ammonia?

NH3

Ionization Energy

Defined as the energy required to remove an electron from the ground state, in the gas phase. Also can think of it as: how much energy do you need to remove an electron from the ground state when something is in the gas phase. In other words, you're starting out with a neutral atom, you're popping off an electron to form a positively charged cation- everything is in the gas phase. And you can technically do this lots of times. Trend: Generally decreases as you go down a group. In other words, it gets easier and easier to remove electrons as you go down. Another trend: Generally increases as you go across a period. In other words, it gets harder and harder to remove electrons as you go across a period.

Which of the following is a correct interpretation of the results of Rutherford's experiments in which gold atoms were bombarded with alpha particles? A) Atoms have equal numbers of positive and negative charges. B) Electrons in atoms are arranged in shells. C) Neutrons are at the center of an atom. D) Neutrons and protons in atoms have nearly equal mass. E) The positive charge of an atom is concentrated in a small region.

E

What is the definition for electron configuration?

Electron arrangement within an atom.

Chemical Properties of Elements

Flame Test - used to identify various metals. Oxidation - Oxidizing agents have a tendency to gain electrons. This property can be correlated with ionization energy, electronegativity, and electron affinity. Cl₂+2l-→2Cl-+l₂ will occur since Cl atoms have a higher (more negative) electron affinity then l atoms (-349 kJ/mol vs. -295 kJ/mol) l₂+Cl-→2l-+Cl₂ will not occur.

How to determine the charge for an ion:

For groups 1A-4A the "usual" charge of an ion is based on its position: +1, +2, +3, +/-4, -3, -2, -1, 0 For group B (transition metals), use the stock system. Roman numerals represent charges. Ex. Fe(II) ion = Fe²+

What is the name for NO2?

Nitrogen Dioxide

What is the name for NO?

Nitrogen Monoxide

What is nuclear stability?

Nuclei can be predicted to be stable/unstable "radioactive" based on the number of nucleons (protons and neutrons). Generally if Z (protons) > 84 the nuclide will undergo radioactive decay. All elements where Z>92 are "artificial" in the sense that they are not naturally occurring. For "small" nuclei, stable configurations are achieved when (A-Z)/Z is 1. For "large" nuclei, (A-Z)/Z is >1 "magic numbers" exist where nuclei are exceptionally stable: 2, 8, 20, 28, 50, 82, 126.

What is a diagonal relationship?

Often the 1st member of a group has properties that are different from the other members of the group, but are similar to those of the 2nd member of the adjacent group. Relatively high charge density. Ex: Li Li2CO3, LiF, LiOH, and Li3PO4 are much less soluble than the corresponding salts of the other alkali metals. Li + N2 → Li3N (other alkali metals don't react) Li + O2 → Li2O (other alkali metals form peroxides or superoxides)

What is an oxyanion?

Oxyanions have a varying number of oxygen atoms as part of the polyatomic ion. To name these polyatomic ions is the endings change, so the one that has fewer oxygens in it gets the ending -ite, and the one that has more oxygens get the ending -ate. The problem with chlorine is there's 4 possibilities instead of 2. SO, we use the middle 2 as the chlorite and chlorate and the first one, has one oxygen less then chlorite does. So, I'm gonna use the prefix hypo- to mean less than. And the last one has one more oxygen, so we use the prefix per-.

Who is Max Planck?

Planck proposed that energy is quantized -- only certain energy levels are allowed. And the way he expressed this was that the energy should be directly proportional to frequency. The constant of proportionality is called Planck's constant (h) = 6.626*10^(-34) Jules*sec

What are the 3 fundamental particles we are focusing on?

Protons, neutrons, and electrons. (neutrons isn't technically a fundamental subatomic particle)

What is the definition for ground state electron configuration?

electron configuration of an atom at the lowest energy level possible.

What will happen to periods (horizontal) on periodic table as you get more and more energy levels?

increase in effective nuclear charge, bc even though you have more electrons, we also have more protons, and so there's a stronger attraction between the nucleus with all of its positive charge and all the electrons with all of their negative charges and they get drawn closer together. This is sometimes called an increase in the effective nuclear charge. There's more of a feel that the electrons on the outside are experiencing due to all of these positive charges in the nucleus.

The 7 SI units of measurement

length (m), mass (kg), time (s), temperature (K), amount of substance (mol), electric current (A), luminous intensity (cd)

Who is Bohr?

responsible for "old quantum mechanics" around 1913 he used a combination of classical physics and this new interpretation for energy to derive "orbits", or energy levels (very similar to a planetary model) Bohr said that photons of light are emitted when electrons go from a higher to lower energy level. Bc the energy levels are fixed, only certain wavelengths of light will be observed.

What is the oxidation number?

the magnitude of the charge

What is electronegativity?

the tendency of an element to gain electrons.

What is atomic mass/weight?

the weighted average of all mass numbers

What info does quantum numbers indicate about an electron?

what "shell" it is in; the shape of the orbital; the spatial orientation and degeneracy of the orbital

Alpha decay

α Loss of helium nucleus - results in ejection of positive particles ⁴₂He (this element has a charge of 2+) Typically occurs with heavier nuclei Ex. ²³⁸₉₂U→⁴₂He + ²³⁴₉₀Th Hint: top number is the mass number (number of protons and neutrons), the bottom number is the atomic number (charge in the nucleus)

Beta (minus) decay

β common for medium-sized nuclides β- decay: loss of an electron Ex. ¹⁴₆C→⁰-₁e+¹⁴₇N Net conversion of a neutron into a proton [(A-Z)/Z too high] ¹₀n→⁰-₁e+¹₁H neutron → electron+proton Hint: if all you see is beta decay, it is assumed to be beta minus decay

Gamma Decay

γ Loss of a high energy photon ⁰₀γ No change in atomic or mass number Ex. ⁹⁹,m₄₃Tc→⁰₀γ+⁹⁹₄₃Tc We can think of the nucleons as being found in various energy levels, just like electrons

How many seconds are in a year?

31,536,000 s

What is a periodic trend?

A pattern that emerges in chemical and physical properties when elements are arranged in the periodic table. Ex. how many valence electrons do you have, how many core or inner shell electrons do you have, and how many protons do you have (nuclear charge)

What does the atomic line spectra show?

A range of wavelengths of light.

Disproportionation Reaction

A redox reaction where the same element is being both reduced and oxidized at the same time. Ex. Hydrogen Peroxide, H₂O₂, the oxygen in it has a charge of -1, or oxidation number of -1. If you leave a bottle of hydrogen peroxide just sitting on a windowsill eventually it's going to turn into water and oxygen gas. In H2O, the oxygen has an oxidation number of -2, whereas the oxygen and oxygen gas has an oxidation number of 0. When they go from -1 to -2, the oxygen got reduced. But when I go from -1 to 0, the oxygen got oxidized. So, it's the same elements, oxygen, that's being reduced and oxidized. Which makes it a disproportionate reaction.

Reactions of Alkali Metals (ex. Li, Na, K, etc)

Alkali metals can react with a number of different substances. Alkali metals can react with halogens (F2, Cl2, Br2, I2). Ex: M + X2 → MX Alkali metals can react with hydrogen. M + H2 → MH Alkali metals can react with excess oxygen. Li + O2 → Li2O (plus some Na2O) Na + O2 → Na2O2 (plus some Na2O) M + O2 → MO2 (M=K, Rb, Cs) Alkali metals can react with water. M + H2O → MOH + H2

What are atoms made out of?

All atoms are made out of different particles, called subatomic particles.

Pauli Exclusion Principle

All electronic wave functions must be antisymmetric under the interchange of any two electrons. It is impossible for two electrons in the same orbital to have the same spin. No two electrons can have identical quantum numbers (in the same atom).

Nuclear fission

Artifical transmutation process that releases a tremendous amount of energy ¹₀n+²³⁵₉₂U→¹⁴¹₅₆Ba+⁹²₃₆Kr+3¹₀n Typically initiated by a "magic bullet", commonly a neutron Notice that for every one neutron that is used, three neutrons are produced. Each of these neutrons can then be used for another fission reaction, and so the reaction leads to an unstable (supercritical) situation since the number of particles grows exponentially. This is known as a chain reaction.

List the following ions in order of increasing radius: Li+, Mg2+, Br-, Te2-.

As a trend, the size of the radius changes depending on whether you're going vertically or horizontally. So generally speaking, as you go down size increases so radius increases. As you go left to right, generally speaking, size decreases and the reason for this has to do with the different kinds energy levels. As you go down you get more and more energy levels. So, the answer should be: Te2-, Br-, Mg2+, Li+

What are ions?

Atoms that have gained or lost electrons (have + or - charge). They can have very different properties than their corresponding elements. Ions can also be polyatomic (composed of more than one atom).

Periodic Trends in Group 13 (B, Al, Ga, In, Tl)

B is a nonmetal/metalloid - forms covalent bonds but displays electrical properties of semiconductors (diagonal relationship w Si) Al is a metal/metalloid - forms covalent bonds but can also lose valence electrons to form ions (Al3+) Ga - forms Ga3+ ions to achieve stable configuration ([Ar]3d¹⁰) In and Tl tend to form +1 ions bc they lose the valence p electrons but nOT the valence s electrons (inert pair)

Why are electrons called electrons?

Bc they were being produced when electricity was generated.

What is a hydrate?

Chemicals that contain H₂O in their formula. The water molecules are actually associated with the cations/anions in a well-defined way. A prefix must be used to indicate the number of H₂O molecules.

Milli (m)

10^-3

Micro (u)

10^-6

Nano (n)

10^-9

Tera (T)

10^12

Kilo (k)

10^3

Mega (M)

10^6

Giga (G)

10^9

What is the correct ground state electron configuration for Fe?

1s²2s²2p⁶3s²3p⁶4s²3d⁶

What are cations?

+ charge/oxidation state/oxidation number (lost electrons). Usually originate from metals.

What are anions?

- charge/oxidation state/oxidation number (gained electrons). Usually originate from nonmetals.

Consider the orbitals shown here in outline. (a) What is the maximum number of electrons contained in an orbital of type (x)? Of type (y)? Of type (z)? (b) How many orbitals of type (x) are found in a shell with n = 2? How many of type (y)? How many of type (z)? (c) Write a set of quantum numbers for an electron in an orbital of type (x) in a shell with n=4. Of an orbital of type (y) in a shell with n=2. Of an orbital of type (z) in a shell with n=3. (d) What is the smallest possible n value for an orbital of type (x)? Of type (y)? Of type (z)? (e) What are the possible l and m sub l values for an orbital of type (x)? Of type (y)? Of type (z)?

(a) No matter what the orbitals look like, the max number of electrons you can have in any of these orbitals is two. (b) x corresponds to an s orbital because it is spherical. y corresponds to a p orbital, bc it looks like a figure eight or a dumbbell. and z corresponds to d orbital because it looks like a flower or like 2 p orbitals together. Within the second energy level we can only have s or p orbitals. There's only 1 s orbital that's possible, but there are 3 different p orbitals that are possible, depending on which way they're facing in space. And as far as the d's go, we don't have any d orbitals in the second energy level, so that's gonna be 0. (c) If it's an s orbital, that means that the second quantum number, the l value, has to be 0. Once I know that l is 0, that also helps me figure out what the third quantum number, the magnetic quantum number, m sub l is. So the rule is that the absolute value of m sub l has to be less than or equal to l. So if l is equal to zero, there's only one possibility for m sub l, which is 0. And then for the spin, spin could either be up or down, which is +1/2 or -1/2. It's arbitrary which wat you start. So let's just make this +1/2, but would've also been correct to make it -1/2. Second part of question: If I know I'm looking in the second energy level, n=2, and I want an orbital of type y, y is a p orbital, that means that l has to be 1. So for m sub l, I've got some choices. M sub l could be 1, 0, or -1. Let's just choose 1. And as far as spin goes, again, I also have some choices: +1/2 or -1/2. Let's choose +1/2. Now, last part of question. Let's say that n is equal to three, and I'm looking at the z orbital, the one that I'm calling z, which is really a d orbital. D orbital means that l=2. And now we have choices for m sub l: 2, 1, 0, -1, or -2. Let's choose -1. Spin: +1/2 or -1/2. Let's choose +1/2. (d) Since I know that I'm dealing with type x orbitals, that's the same as an s orbital, which means that l=0. And these s orbitals can exist in any of the energy levels. So I could still have this in the first energy level or the second or the third or the fourth. But since the questions was the smallest possible one, I can have s orbitals in just the first energy level, which would be one s. If I'm dealing with type y, that's the p orbital, that's where l=1. I don't have p orbitals in the first energy level, but I do have them starting in the second energy level. The smallest value would be 2. And then similarly for type z, this is a d orbital, where l=2, this doesn't exist until the third energy level and beyond, so the smallest one would be n equals three. (e) We decided that the first orbital, orbital x, had an l value of zero. Now the value of m sub l has to follow this relationship, absolute value of m sub l is less than or equal to l. So since l=0, m sub l=0. If I look at orbital y, here I have some other possibilities. I know that absolute value of m sub l, again, is <=l. If l=1, m sub l could be 1, 0, or -1. And then finally, for l=2, use the same inequality. Now I have 5 possibilities for m sub l, can range anywhere from 2 to -2.

The 4 different quantum numbers in an atom

1. Principal quantum number (n). Same as Bohr's energy levels. n tells you what shell, or what energy level, the electron is in. 2. Angluar momentum quantum number (l). l depends on n. l has to be <= n-1. l is an orbital. Ex. l=0→s orbital, l=1→p orbital, l=2→d orbital, l=3→f orbital 3. Magnetic quantum number (m sub l). Rule for determining the value for this: the absolute value of m sub l has to be less than or equal to l. The physical significance for this magnetic quantum number is that it tells you spatial orientation and degeneracy of the orbitals. Degeneracy means how many different ways can you have the same exact energy, but different orientations. For example, if you look at the p orbitals, l=1 but m sub l = either 1, -1, or 0. 4. Spin quantum number (m sub s). Unrelated to the other 3 quantum numbers. It has to do with spin coordinate. Spin uses half integers. For example, 1/2 or -1/2

Rule for naming compounds:

1. Usually put metal first, then nonmetal (go from left to right from the periodic table). If you are unsure which is the metal and which is the nonmetal, or if you have 2 nonmetals together, or two metals together, then just go from left to right. Exceptions - N, H, O. You always put N first, then H, then O. 2. Name = firstelement secondelement(-ide) 3. Prefixes: ionic substances generally have no prefixes; prefixes for covalent substances are always used for the 2nd element, even if it only has one of them, but are only used for the 1st element if >1

6 Significant Figure Rules

1. any non-zero digit is significant (ex. 1234) 2. zeros sandwiched between digits are significant (ex. 1023) 3. zeros to the left of a decimal point aren't significant (ex. 0.123) 4. zeros to the left of the first non-zero digit aren't significant (ex. 0.0000123) 5. zeros to the right of the last non-zero digit are significant (ex. 0.123000) 6. if there is no decimal point, zeros are not significant (ex. 100 vs. 100.)

Pico (p)

10^-12

Femto (f)

10^-15

Centi (c)

10^-2

Redox reactions

Redox is a combo of a reduction and an oxidation. A reduction is a chemical reaction where electrons are gained, and an oxidation is a chemical reactions where electrons are lost. So, reductions cause the oxidation numbers to go down, to become more negative or less positive. Whereas oxidations make the oxidation numbers increase. So, redox reaction is really just a combo of a reduction reaction and an oxidation reaction that both happen at the same time.

Reactions of Alkaline Earth Metals

With halogens (F2, Cl2, Br2, I2): M + X2 → MX2 With nitrogen: M + N2 → M3N2 With oxygen: M + O2 → MO With water: Mg + H2O(g) → MgO + H2 M + H2O → M(OH)2 + H2 (M does not equal Mg)

Explain why the H2O molecule is bent, whereas the BeH2 molecule is linear.

So to do this, it would help if I drew the Lewis structures for each of these. Looking at the periodic table, we can see that hydrogen has 1 valence electron, beryllium has 2, oxygen has 6. H2O: 2(1)+6 = 8 total electrons BeH2: 2(1)+2 = 4 total electrons So now here's where the different shapes come in. If I look at the structure for water, it has these extra lone pairs in it that the structure for beryllium hydride did not and that makes all the difference. Bc if I look at H2O, I have a total of 4 electron groups, 2 bonded pairs and 2 not bonded pairs, which means that it's gonna be the tetrahedron family, but actually gonna be a bent geometry, so that the angles between the atoms and gonna be approx 105 degrees. In contrast, if you look at beryllium hydride, there's only two things, or two electrons groups surrounding the beryllium atom, which means this is gonna be linear geometry, so the angle between the H, the Be and the H will be closer to 180 degrees, so that's why they have different shapes depending on the number of lone pairs, or pairs of electrons that are surrounding the central atom.

Electronegativity (EN or greek letter chi)

Tendency of an element to gain electrons. Related to ionization energy and electron affinity. Bc they're based on ionization energies and electron affinities, they have the same trend as ionization energy and electron affinity, meaning that typically electronegativities increase as you go across, and they decrease as you go down.

Effective Nuclear Charge

Z sub eff is meant to incorporate the shielding effect of core (inner) electrons.

What did Rutherford do?

The gold foil experiment. Rutherford proposed that each tiny atom has a center called the nucleus that takes up the majority of the mass of the atom. All the protons and neutrons live in the nucleus, and electrons live on the outside, bc electrons are much lighter. This experiment helped develop our current understanding of an atom.

Where does the atomic number of an elements come from?

The number of protons it has.

What didi Millikan do?

The oil drop experiment. Used x-rays to produce electricity/current for experiment. Used an atomizer. He got the actual numbers for the mass and charge of the electron. Mass: 9.11*10^(-31) kg Charge: -1.602*10^(-19) coulombs

What is the period number on a periodic table?

The period number tells me the principal quantum number or the n value. So for example, everything in period 3 has its valence electrons in the third energy level. Period numbers go horizontal.

What is the mass number?

The total number of nucleons (number of protons and neutrons which are in the nucleus) in the atom.

What is a polyatomic ion?

Think of a polyatomic ion as a cluster, a collection of atoms, and then, that whole thing, net, has a charge that can either be positive or negative, depending on what's going on. Look at picture for a table of some polyatomic ions.

Ionic Radius

This is a periodic trend. Defined like we would define atomic radius. It's how big an ion is. Similar trend as an atomic radius as well. Ionic radii for metals are smaller than those of the corresponding atomic radii. Ionic radii for nonmetals are larger than those of the corresponding atomic radii.

What is a formula unit?

This term is used to describe ionic compounds. It represents the smallest collection of ions that combine to form something neutral. Ex. NaCl, Al₂O₃ In naming formula units, prefixes are NOT used.

Write the Lewis structure for SeCl3+.

^ valence electrons from selenium, and 7 from each of the chlorines. But I also know that the thing has a charge of +1, which means that it lost an electron, so we subtract 1 from this. 6+3(7)-1=26 total electrons Step 1: Put an atom in the middle. An essential atom is, generally speaking, the one that is written to the left of the molecule, so in this case, it's selenium, and then we connect the selenium, and then we connect the selenium to the chlorines by using single bonds. Cl - Se - Cl | Cl So each of these single bonds is really a pair of electrons. So, if I keep track of what I had, I had 26 electrons total. I used up six bc I have 3 bonds, each of which is 2 electrons, that leave me with 20 electrons. Now I distribute the electrons to the outer atoms so that they have a stable octet. So that means that each Cl will get 6 more electrons so each one can add up to 8. That uses up 18 of my 20 electrons. So, I have 2 left. I'm going to distribute those to the central atom. We can check to see if we have the right answer by figuring out the formal charge for each of the atoms. The formal charge for any of these is equal to the number of valence electrons minus the number of bonds that I have, minus the number of nonbonded electrons. Se = 6 valence electrons - 3 bonds - 2 nonbonded electrons = +1 charge Cl = 7 valence electrons - 1 bond - 6 nonbonded electrons = 0 Add up all the charges = 1 + 3(0) = +1 total charge

What is a neutralization reaction?

acid + base → salt + water Ex. HCl (aq) + NaOH (aq) → NaCl (aq) + H₂0 (l)