DAT General Chemistry Mike's Chapter 4 (Periodic Trends)
Where are the metals in the periodic table?
Metals are groups 1 (excluding Hydrogen, 2, all of d block and f block, and of the p block: Al, Ga, In, Sn, Tl, Pb, Bi and Po
What are the characteristics of noble gases?
Noble gases are inert (unreactive) elements. This is because they have a fully octet and are happy.
Where are the metalloids?
Stair step down to the right starting with B: B, Si, As, Te, AT and also Ge, Sb
Where is the oxygen group ("Chalcogens") located on the periodic table?
The Chalcogens are located in Group 6A (Or 16) of the periodic table.
Where are the Alkaline Earth Metals located on the periodic table?
The alkaline earth metals are located in group 2 (column 2) of the periodic table.
Electron Affinity:
The amount of energy released (in kJ/mole) by a neutral atom (in the gaseous phase) when an electron is added to the atom to form a negative ion. (Note: because it is energy RELEASED, electron affinity is a negative value). Energy is negative because its an exothermic reaction. (Remember that ionization energy is the amount of energy required to remove one or more electrons from an atom. If removing electrons COSTS energy, then adding electrons should PRODUCE energy. Indeed, this is generally the case. this energy that is produced (aka released) when an atom accepts an electron is called its electron affinity). *A large electron affinity value means that a large amount of energy is released when an electron is added to the atom. *A small electron affinity value means that a small amount of energy is released when an electron is added to the atom.
Ionization Energy:
The amount of energy required to remove the most loosely bound electron (valence electron) to form a cation. It stills takes energy to remove an electron even if the element really wants to lose their outermost electron (like Na) *Therefore, a LOW ionization energy means that little energy is needed and thus the electron is easily discharged from the atom. *Therefore, a HIGH ionization energy means that a lot of energy is needed and thus the electron is not easily discharged from the atom.
What is electron affinity?
The energy produced, or given off, when an atom accepts an electron (like the opposite of ionization energy)
Where are the halogens located on the periodic table?
The halogens are in group 7A (or 17 if counting d-block) of the periodic table.
Effective Nuclear Charge:
The net positive charge experienced by valence electrons, protons ability to pull electrons in As Zeff increases, size decreases *This relates to atomic radius trends: Atoms tend to get larger as you go down a group because higher energy n shells means a larger size. However, in a period, the energy shell n value does not change! This means that the change in size as you move across a period is not due to the energy shell. Rather, the number of protons changes. Because the number of protons per atom increases as you go from left to right across a period, the net positive charge experienced by the valence electrons increases, and the electrons are pulled in closer to the nucleus (Aka the effective nuclear charge increases).
Where are the noble gases located on the periodic table?
The noble gases are located in Group 8 (Column 18) on the periodic table.
Electronegativity:
The tendency of an atom to attract electrons. *Therefore, high electronegativity means that the atom has greater tendency to attract electrons. *Therefore, low electronegativity means that the atom has a lower tendency to attract electrons.
Where are the transition metals located on the periodic table?
The transition metals are generally located in the d-block of the periodic table.
What are the two forms of molecular oxygen and what is their reactivities?
There are two forms of molecular oxygen: O2 and O3. O2 is a good oxidizing agent (oxidant) (meaning it likes to steal electrons from other substances) and O3 (Ozone) is an even better oxidant. Because of molecular oxygen's desire to accept electrons form other substances, metals (which tend to like to get rid of electrons) like to react with oxygen to form metal oxides. This is especially true of metals in groups 1 and 2 When metal reacts with molecular oxygen (such as O2), the following reaction type occurs: M(s) + O2 (g) --> MO(s) MO is metal oxide
True or false: Metals constitute the majority of elements:
True
Why does Nitrogen have a higher ionization energy than Oxygen?
Uncharged nitrogen has a half full 2p shell, so it is more energetically unfavorable for nitrogen to lose an electron compared to oxygen, which, if it was to lose an electron, would gain the stability from a half full 2p orbital
How do we determine the number of electrons that a NEUTRAL atom has?
When neutral, an element's number of electrons is equal to the number of protons. The number of protons is called an element's atomic number. Therefore, the number of electrons is equal to the element's atomic number.
The larger the atoms, the farther they will be from each other, and the weaker the bond between the atoms will be. Thus, bond strength increases with decreasing size of the halogen. Atomic size increases down a group. So, H-Br is the weakest bond and H-F is the strongest.
bond dissociation energy is basically bond strength. The smaller the bond the higher the bond dissociation energy. This all comes to size of atoms. Smallest atoms will have the strongest bonds.
The protons ability to suck electrons is called
effective nuclear charge (Z eff). Effective nuclear charge increases as you go left to right on periodic table because the number of protons are increasing so they suck electrons even more.
Is there electronnegativity for noble gases? is there electron affininty for noble gases? is there ionization energy for noble gases?
nope nope yus
Do noble gases have electronegativity?
nope, they have perfect number of valence electrons (8) so they DO NOT HAVE electron negativity
When you are writing hte electron affinity equation of an atom, even if there is a diatomic molecule you need to write it as
one atom for exaple: chlorine electron affinity equation is not cl2 + e- = cl2 - it is, cl + e- = cl-
As protons go ______ effective nuclear charge (Zeff) goes _______ and size goes _______
up, up, decreases down, down, increases
What are the 6 important groups of the periodic table, that you should know for the DAT?
(1) Alkali Metals (Group 1) (2) Alkaline Earth Metals (Group 2) (3) Halogens (Group VIIA) (4) Noble Gases (Group VIIIA) (5) Transition Metals (d-block) (6) Oxygen Group (Group VIA)
What are noticeable exceptions to the electron affinity trends?
(1) Be has an electron affinity around 0 because it has a filled 2s subshell: doesn't want to gain or lose an electron (2) N has an electron affinity around 0 because it has a half filled 2p subshell, with all 2p electron unpaired. It likes this because all electrons are unpaired in p.
What are the six Alkaline Earth Metals?
(1) Beryllium (Be) (2) Magnesium (Mg) (3) Calcium (Ca) (4) Strontium (Sr) (5) Barium (Ba) (6) Radium (Ra)
What are the five halogens?
(1) Fluorine (F) (2) Chlorine (Cl) (3) Bromine (Br) (4) Iodine (I) (5) Astatine (At)
What are the six noble gases?
(1) Helium (He) (2) Neon (Ne) (3) Argon (Ar) (4) Krypton (Kr) (5) Xenon (Xe) (6) Radon (Rn)
What are the characteristics of the halogens?
(1) Highly electronegative (2) High electron affinities (3) Reactive with metals and good oxidizing agents Halogens are easily reduced (Halogens are only one valence electron away from having a full octet. Thus they easily add electrons and a lot of energy is released when the electron adds). Because halogens are easily reduced (easily gain electrons), and because metals are easily oxidized (easily lose electrons), halogens are highly reactive with metals and are good oxidizing agents
What are the six Alkali Metals?
(1) Lithium (Li) (2) Sodium (Na) (3) Potassium (K) (4) Rubidium (Rb) (5) Caesium (Cs) (6) Francium (Fr)
What are the characteristics of Alkali Metals (3)?
(1) Low ionization energies (aka easy to remove an electron from them). -This is because they want to lose their outermost electron so they can shift to the left and feel like the nearest noble gas. (In other words, it is easier to shift left than right for elements in Group 1) (2) Very reactive with water -Note: When alkali metals react with water, the following reaction type takes place: M(s) + H2O(l) --> MOH(aq) + 1/2H2(g) [The alkali metal reacts with water such that metal hydroxide and hydrogen gas are produced. During this reaction, the hydrogen in H2O is reduced to H2 gas] [This reaction is very exothermic] (3) Readily form ionic compounds with non-metals. (Remember, the metal [in these cases, alkali metals] give away electrons to non-metals])
What are the characteristics of the Alkaline Earth Metals (2)?
(1) Low ionization energies (but not as low as the alkali metals) (meaning they are easily stripped of electrons) (2) React with water -Not as violently as the alkali metals. -Generally, they get more reactive with water as you DOWN the group.
What are some of the noticeable exceptions to the ionization energy trends:
(1) N has a higher ionization energy than O even though O has a higher electronegativity. (2) Be has a higher ionization energy than B even though B has a higher electronegativity.
What are the five Chalcogens?
(1) Oxygen (O) (2) Sulfur (S) (3) Selenium (Se) (4) Tellurium (Te) (5) Polonium (Po)
Group (Periodic Table)
-A group is a column on the periodic table -Elements of the same group (column) tend to have similar properties.
Period (Periodic Table)
-A period is a row on the periodic table -Elements of the same period (row) do NOT necessarily have similar properties.
Atomic Radius:
-An atom's radius (the distance from its nucleus to the outside of its outermost orbitals) -Helps convey the size of the atom's electron cloud.
Electron Affinity Trends:
-Electron affinity (aka energy released due to the addition of an electron) tends to increase as you move right across a row -Electron affinity (aka energy released) tends to increase as you move up a column *Note: Noble gases are excluded from the electron affinity trends.
How do you compare the size of different ions of the SAME element?
-If you give an atom an electron, the atom increases in size. -If you take an electron away form an atom, the atom decreases in size. Therefore, the more electrons an atom has, the larger the atom, and the less electrons an atom has, the smaller the atom. Therefore, when comparing ions of the SAME element, we can rank the ions by size based solely based on their number of electrons because all else is equal. Ex: Of O, O-, O2-, and O+, O2- is the largest and O+ is the smallest because O2- has the most electrons and O+ has the least number of electrons.
Atomic Radius Trends:
-In general, atomic radius get SMALLER as you go to the RIGHT across a row or UP a column on the periodic table. Thus atoms tend to get LARGER as you go LEFT across a row or DOWN a column on the periodic table (includes noble gases) -Francium is the largest element and Helium is the smallest.
Ionization Energy Trends:
-Ionization energy tends to increase as you go up columns and tend to increase as you go right across a row. -The ionization energy rends DO include the noble gases! Electron neg. DO NOT get included -Opposite trend of atomic radius because as an atom gets smaller, its more difficult to remove an electron because the electron is closer to the positively charged protons in nucleus
Bond Length:
-The distance between the nuclei of two atoms when the two atoms bond -Bond length is therefore equal to the atomic radius of the first atom + the atomic radius of the second atom.
What are the characteristics of transition metals?
1) They often form brightly colored compounds, due to the funky way that d orbitals allow their electrons to absorb colored light and be promoted to higher-energy levels 2) Can have multiple oxidation states (Iron can be -4 - +6
Isoelectronic Series:
A group of atoms or ions that are from DIFFERENT elements but that all have the same number of electrons. Ex: O2-, F-, Ne, Na+, and Mg2+ are an isoelectronic series because, even though they are all atoms of ions of different elements, they all have the same number of electrons (in this case 10 electrons).
Where are the Alkali Metals located on the periodic table?
Alkali Metals are found in Group 1 (Column 1) of the periodic table.
Where are the non-metals in the periodic table?
All of the elements to the right of C, P, Se, I and Rn
First, let's make sense of the data given in the question - we should notice that when carbon is given an electron, it has an enthalpy of -154 kJ/mole, meaning that process emits 154 kJ/mole of heat energy. When nitrogen undergoes the same process, ΔH = -7 kJ/mole, so it only emits 7 kJ/mole of heat energy. What does this mean? This means that adding an electron to an atom of carbon has a much more stabilizing result than adding an electron to nitrogen. Thus, carbon has a higher electron affinity than nitrogen.
And so this is why Be and N have electron affinities close to zero. When the get an electron not alot of energy is released cuz they dont really like it. When electron accpetance is favored then alot of energy is released.
The atom's atomic radius is measured in _______________ units.
Angstrom
As we go from left to right on the periodic table, do we get higher energy shells? What do we get? And what does it do
As we go from left to right on the periodic table, the energy of the shell stays the same (n). For example look at period 2. The s block is 2s, and the p block is 2p. ENERGY level of the shell staying same as long as n=2 stays same. The size of the shell stays the same. As we go from left to right on the periodic table, the number of protons increase. More protons mean that more protons will suck the electrons so the size will get smaller.
Why do we see the atomic size trends that we see?
Atoms get larger as you go down a group because n of the orbitals increases (1s, 2s, 3s, 4s), the higher energy orbitals are bigger: means a larger size. Atoms get smaller as you go across a period from left to right because an increase in effective nuclear charge means a smaller size.
II. An atom with electron configuration 1s2 2s2 2p6 3s2 will form a stable -2 ion.
Atoms lose or gain electrons forming ions so that they will have an electron configuration of a noble gas. An atom with the electron configuration 1s2 2s2 2p6 3s2 can give up 2 electrons to have an electron configuration of 1s2 2s2 2p6 = [Ne]. Therefore, it will form a stable +2 ion, rather than a -2 ion. A -2 ion of this atom would imply the gain of 2 electons, and the electron configuration would instead be 1s2 2s2 2p6 3s2 3p2, which is even further from a desired noble gas electron configuration (octet). This is why II is false.
Why does ionization increase as you go top right?
Because as size decreases, the electrons are way closer to the nucleus so it is harder to remove them therefore the ionization energy (amount of energy needed to strip an electron) INCREASES. As size increases the electrons are way further so the amount of energy needed to strip those electrons get smaller. IONIZATION ENERGY DECREASES AS size increases.
Why does Beryllium have a higher ionization energy than Boron?
Beryllium has a full 2s shell, and Boron has one electron in the 2p shell, so the extra stability that comes with a full shell makes it more energetically unfavorable to strip an electron from beryllium than from Boron, which would gain some stability if it were to lose an electron
What is the oxygen group called?
Chalcogen
Despite the trends, which element has the largest electron affinity value?
Cl (not F)
What is the difference between electronegativity and electron affinity?
Electron affinity correlates to electronegativity just as many other periodic trends correlate to each other. While electronegativity is the ability of an atom to gain an electron, electron affinity is the energy release that occurs when an electron is gained. When an atom gains electrons, energy is released. The amount of energy released is measured in kJ/mol.
What type of reaction does electron affinity represent?
Electron affinity represent an exothermic reaction (meaning a negative ∆E, meaning a reaction in which energy is produced. The more negative the ∆E of the reaction, the more favorable the reaction)
True or False: Because the members of an isoelectronic series all have the same number of electrons, they all have the same size.
False: Even though the members of an isoelectronic series have the same total of electrons, they can be different sizes. Remember that the effective nuclear charge is the net positive charge experienced by valence electrons. Thus, even though the size might be the same if solely based on the electron number, the more protons the atom/ion has, the more attraction is felt by the electrons, and the smaller the size). Ex: O2-, F-, Ne, Na+, and Mg2+ is ranked by size as (Mg2+) < (Na+) < (Ne) < (F-) < (O2-) where Mg2+ is the smallest and O2- is the largest. Thus IN AN ISOELECTRONIC SERIES, to determine size difference consider the effective nuclear charge and thus the number of protons.
What element has the highest electronegativity?
Fluorine (F)
What is the trend for electron affinity?
Follows that of electronegatively, gets larger and more negative (so more favorable) as you go up and to the right, with noble gases excluded, except Cl has the highest electron affinity, not fluorine
What is the bond length between two identical atoms?
For any bond between atoms of the same element (or in which the atomic radii of the two elements are equal), the bond length = 2 X atomic radius. When different sized atoms bond, this is not true because the atomic radius is not the same for both. One can have a bigger atomic radius then the other. For identical molecules, the atomic radius is equal so you can multiple it by 2 to bin d bond length.
What are metalloids?
Halfsies between characteristics of nonmetals and metals - B, Si, Ge, As, Sb, Te, At, staircase at aluminum
Electronegativity Trends:
Increases as you move to the right and up. Note: The noble gases are NOT electronegative because they do not want electrons. Therefore, they are not included in the general electronegativity trends.
Successive Ionization Energies:
It is possible to remove more than one electron from an atom, therefore an atom's first ionization energy is the amount of energy required to remove its first electron; an atom's second ionization energy is the amount of energy required to remove its second electron, and so forth. Each successive ionization energy (first, then second, then third, etc.) is larger than the previous meaning each successive electron lost requires more energy. However, once an atom "feels" like a noble gas, the ionization energy required to remove any electron from this stable state is VERY large
