Chemistry Final

Identify and explain the three rules used to determine an atom's electron configuration.

-Aufbau principle: Electron will occupy the lowest energy orbital that can receive it -Pauli exclusion principle: Electrons in an orbital must have opposite spins and it limits to 2 -Hund's rule: Orbitals of equal energy each occupied by one electron before it is occupied by a second electron and all electrons in singly occupied orbitals must have the same spin

What are the 5 parts of Dalton's Atomic Theory?

-Matter is composed of atoms -Atoms of given element are the same -Atoms of different elements aren't -Atoms can combine with atoms of other elements (compound) and the same compound has the same proportions -Atoms are indivisible in chemical processes.

What is a bond dipole? Molecules with which type of bond will form a bond dipole Which of the molecules above would exhibit a bond dipole?

A bond dipole is the separation of positive and negative charges in a chemical bond. A molecule must have an ionic or polar covalent bond to have a dipole.

Distinguish between a bond dipole and a molecular dipole. Is it possible for a molecule to have bond dipoles, but not a molecular dipole? Explain.

A bond dipole is within a chemical bond, while a molecular dipole is the whole molecule having a split of positive and negative charges. Molecular dipoles are diatomic molecules with polar covalent bonds.

Distinguish between homogeneous and heterogeneous mixtures. Provide examples of each.

A heterogeneous mixture has two or more phases (water and oil). A homogeneous mixture will be evenly distributed (salt and water).

What is a molecule?

A molecule is the smallest unit of a covalently bonded compound that retains the properties of its larger compound. It is not limited to compounds but can be covalently bonded atoms of the same element.

What is a pure substance?

A sample of matter, either a single element or a single compound, that has definite chemical and physical properties

What is electron shielding?

All electrons have a negative charge and repel each other, nucleus is positive and electrons have attraction. Core electrons shield nuclei from the pull of valence electrons.

What do all elements in a group have in common?

All elements of a group have similar chemical properties, as well as they have the same number of valence electrons.

Describe how an ionic bond forms. In your description include the terms anion and cation.

An ionic bond is formed when there is a complete transfer of electrons from metal to a non-metal. After the loss of that electron metal will form a cation and the nonmetal will form an anion after gaining the electron

What is an ionic compound? Why aren't they referred to as molecules?

An ionic compound is composed of positive and negative ions that are combined so that the number of positive and negative charges are equal. They aren't referred to as molecules because they don't form individual compounds like those that use covalent bonds.

What is an orbital as described by the wave mechanical model?

An orbital is the area where you have 90% probability of finding electrons. It is the three dimensional state, a single sphere and can build many shapes.

Describe the trends in atomic radius that can be observed on the periodic table. Relate these trends to principal energy level and electron shielding.

As you go across the period of a periodic table the radius decreases, this is due to the fact that the nucleus and valence electron attraction grows making the bonds stronger and pulling the electrons closer. As you go down the group the radius increases because the valence electrons remain the same, but the nucleus continues to change therefore spreading the atom further apart, weakening attraction.

Distinguish between atoms and elements.

Atoms are the smallest unit of an element that maintains chemical property of the element. While the element is matter composed of a single type of atom and can't be broken down.

Explain why atoms bond in terms of potential energy.

Atoms have high potential energy and it is minimized once they bonded. However, before the bond as they close in on each other their potential energy becomes even higher. With a minimized energy they are more stable.

What is bond energy? Why can it be used as a measure of the amount of PE lost during bond formation?

Bond energy is when 2 atoms form a bond and they release energy that is equivalent to the drop in potential energy. It measures the amount of PE because it is the same, the same amount of energy that is released must be put back in to break that bond.

What is the duet rule? Why does it work?

Bonding of 2 hydrogen atoms allows each atom to have stable electron configuration, this is because they only have a single orbital making it different from the noble gas configuration but just as stable.

Covalent and ionic bonds are often discussed as if they are two different things, but in reality they are part of a continuum. Explain why.

Both covalent and ionic bonds are ways to hold together atoms, the difference comes from whether they share or transfer electrons. The difference is just a variation from the same concept.

What did Victor De la Broglie demonstrate about the electron?

Broglie proved mathematically that electrons were typically thought of as waves behave as particles and envisioned the bohr model.

What is a chemical bond?

Chemical bonds hold a group of 2 or more atoms together and makes them function as a unit.

What does chemistry study?

Chemistry is the study of composition, structure, and properties of matter.

For a given element, how do the first, second, and third ionization energies compare to one another? Explain why. What happens to ionization energy after all of the valence electrons have been removed?

Compared to the second and third ionization energies the first takes a lot lower amount of energy needed to remove the first valence electron. The attraction on the remaining will increase making it more difficult, once all valence electrons are gone there is a dramatic increase in energy required to remove the core electrons.

Distinguish between the composition of matter and properties of matter.

Composition of matter is the components of a sample of matter relative to the proportions while properties of matter distinguish the qualities or attributes of a sample of matter.

What are compounds?

Compounds are substances made from the atoms of two or more elements joined chemically.

Compare the electrical conductivity of ionic and covalent compounds.

Covalent compounds don't conduct electricity unless they are polar, while ionic compounds can conduct electricity when dissolved in water. The water molecules separate ions and allow them to move and therefore conduct electricity.

Describe dipole-dipole forces.

Dipole-Dipole forces are the attraction of permanent dipoles. They are attracted to each other because of the partial charges, and the molecules will align themselves to maximize the force between the two.

Ionic compounds are hard and brittle at room temperature. Explain why.

Due to the use of the crystal lattice structure when an ionic compound is struck they shift and this causes like charges to break the arrangement and repel each other. This causes the structure to fall apart.

Distinguish between electron pairs and electron regions.

Electron pairs would be the electrons that are bonding and the lone pairs that remain unbonded. The electron region is the number of regions of electron density that determines electron regions around the central atom (lone pairs, bonding pair, and double bonds).

Describe how emission spectra are formed

Emission Spectra is formed when an element can be excited by a strong electric current until it releases light.

What is the Law of Conservation of Energy?

Energy can neither be created nor destroyed it will be transformed and released in light or heat during a chemical reaction.

Relate changes in energy to changes in the state of matter.

For a solid to become a liquid it would have to melt and release energy, for the liquid to become a gas through vaporization with the increase in energy, and from a fas to a plasma it would have to go through ionization and gain energy. Plasma to gas would be dionazation, from gas to liquid would be condensation, liquid to solid would be freezing. From a solid to a gas would be sublimation and a gas to solid would be deposition. FOR A CHANGE OF MATTER MUST BE A CHANGE IN ENERGY

What did the Bohr model get right?

For the hydrogen spectrum it was correct, but it didn't address interactions. It correctly described the energy levels

What is the frequency of electromagnetic radiation?

Frequency of electromagnetic radiation is the number of waves that pass a fixed point in space in a second. They are measured in hz.

Identify and describe the atomic model proposed by Thomson.

He described the Plum Pudding Model which was a positive cloud filled with 1800 randomly spaced electrons and the mass of the sphere was positively charged. The number of electrons equals atomic number.

What unique properties does hydrogen bonding create in water?

Hydrogen bonding creates the unique properties in water of having a high boiling point and strong cohesion.

What distinguishes hydrogen bonds from other dipole-dipole forces?

Hydrogen bonds are when hydrogen is bonded to N, O, F, or CI and the hydrogen in a polar molecule is attracted to the lone pair of electrons in a second polar molecule. The difference between the two would be that hydrogen bonds are with the lone pair and dipole-dipole are with partial charges.

Why is hydrogen considered unique?

Hydrogen is considered unique because its outermost orbital is full, so technically it should be in noble gas configuration however because it only has one orbital it is not located with the others on the periodic table. It makes it just as stable, but unique in location belonging to the s group.

How many electrons can occupy a single orbital? Explain why.

In a single orbital there can hold at most 2 electrons. This is because of the repulsion of like charges of the electrons.

In general, how do the boiling point and melting point of ionic compounds compare to the boiling and melting point of covalent compounds?

In general the boiling and melting points of ionic compounds are much higher than that of the covalent compounds.

Describe how an induced dipole occurs. Would an induced dipole be more likely to occur in an atom with a larger or smaller atomic radius? Explain

Induced dipole occurs when a negative charge on the polar repels the electrons on the non-polar therefore distorting the electron cloud. It is more likely to occur on an atom of greater size this is because with greater distance the strength of attraction is weaker making it easier to distort.

Distinguish between intensive and extensive properties of matter.

Intensive properties are not dependent on the amount of substance/properties the remain unchanged by changes in amount of substance (melting point or color). Extensive properties depend on the amount of substance (mass and volume).

Distinguish between intermolecular forces and intra-molecular forces. Compare them in terms of strength.

Intermolecular forces are the forces acting between molecules and are much weaker compared to intramolecular forces. Intramolecular forces is the force holding molecules together and is within the atom.

What is ionization energy? Describe the trends in ionization energy that can be observed on the periodic table.

Ionization energy is the energy required to remove an electron from an atom in its gas form. To overcome the attraction the energy has to be put in enough to free the electrons. It measures the tendency of natural atoms to resist losing electrons.

How does the Bohr model differ from Rutherford's model of the atom?

It accounts for the electrons ability to move and corrects the problems that were present in the Rutherford model.

How does the wave mechanical model relate to the similar properties seen in the elements in a group or family of elements?

It explains that all atoms are arranged by primary levels as well as sub levels, and the properties of the electrons/ orbitals. It is the electrons that are responsible for the similar properties as the valence electrons remain the same for the entire group or family.

Identify and describe the subatomic particle discovered by JJ Thomson. Explain how he discovered it.

JJ Thomson discovered the subatomic particle by applying voltage to electrodes separated by distance. He used the ray tube and the particles could be deflected from negative charges meaning they were negatively charged.

Identify and describe the subatomic particle discovered by James Chadwick. Explain how he discovered it.

James Chadwick was looking into the ideas of neutrons. He fired alpha particles at Be and the mass of the particles were discovered. The particles couldn't be deflected by a magnet or electric change proving the presence of neutrons.

Explain London dispersion forces.

London dispersion is the weakest of molecular attractions, and serves as a way for non-polar molecules to have intermolecular attractions. When two nonpolar molecules interact with one another an instantaneous dipole can create an induced dipole and they are attracted to one another.

Which elements are considered to be main group or representative elements?

Main group elements are the s and p blocks, they are the elements that gain or lose electrons to try and achieve noble gas configuration.

Distinguish between mass and volume.

Mass is the measure of the amount of matter an object contains while volume is the measure of the amount of three dimensional space that an object occupies.

What defines matter?

Matter is anything that has mass and occupies space.

What is electronegativity and explain the trends in electronegativity seen in the periodic table?

Measure of the atoms of one element's ability to attract electrons from another in a different compound. Trends for the periodic table are as you go across the period it increases because of the decrease in radius causing stronger attraction. Trends down a group will decrease as the radius is increased.

Describe metallic bonding. Include an explanation of delocalized electrons and the sea of electrons.

Metallic bonding is when vacant orbitals in metal atom's outer energy levels overlap and hold the compound together. The overlap allows electrons to roam freeling throughout the entire metal. Delocalized electrons are when electrons separate from their parent atom and enter the sea of electrons which are where the free roaming electrons flow over all atoms in the structure.

What are molecular compounds?

Molecular compounds are individual units that exist on their own. NaCl would be a molecular compound.

Distinguish between electronic geometry and molecular geometry. What is the relationship between the two?

Molecular geometry is the 3D dimensional arrangement of the atoms in the molecule, it is determined by the electronic geometry. The electronic geometry is the arrangement of electron regions around the central atom, with 5 basic geometries based on the number of regions.

What are molecules?

Molecules are the smallest unit of covalent bonded compound that retains the properties of compound, it's not limited to compounds they can be for covalent bonded atoms of the same element.

Explain why noble gases are unreactive. Your explanation should include a discussion of the orbitals in the valence shell of the atoms.

Noble gases are unreactive because they are the most stable. The outermost orbital on their configuration is filled with the maximum number of electrons, so it doesn't need to interact with other atoms to gain or lose any.

Distinguish between periods and groups (aka families) on the periodic table.

Periods are the horizontal rows on the table. The physical and chemical properties change somewhat regularly across periods, the number corresponds with the principal quantum number of electrons in period. Groups are the vertical columns and each group has elements with similar chemical properties.

Distinguish between physical and chemical changes of matter. Provide examples of each.

Physical changes of matter are the changes in matter with the changing of the identity of the matter (cutting and change of state). The chemical changes are the changes in which one or more substances change in chemical composition (color change or release of light/heat)

Distinguish between physical and chemical properties of matter. Provide examples of each.

Physical properties of matter are characteristics that can be observed and measured; they don't affect the identity of substance (color or malleability). Chemical properties are the characteristics that give matter the ability to undergo a change that alters composition, ability to change (energy or reactivity).

What are 4 signs that a chemical change has occurred?

Release of gas Solids are formed from liquid Energy change to hear or light released Color changes

Identify and describe the subatomic particle discovered by Ernest Rutherford. Explain how he discovered it.

Rutherford tested the plum pudding model, using alpha particles. He used radioactive elements such as uranium or radium. He discovered the presence of the nucleus proving the plum model incorrect. He concluded during his gold experiment that the nucleus takes up little space in the middle of the atom and had greater mass. Introduced the idea of protons and neutrons.

Describe the atom as envisioned by Rutherford. What did he get right? What was wrong with the Rutherford model of the atom?

Rutherford's atoms had the small dense nucleus with its protons and neutrons. He believed that the nucleus takes up 99.9 % of the mass but barely any of the volume. The electrons have negligible mass and are found outside of the nucleus and 99% of the volume. The number of protons and electrons are equal to each other and each element has a unique number of protons. He got a lot right, however electrons are moving and charge particles so they should be giving off energy reducing speed and crashing into the nucleus.

Identify and describe each state of matter.

Solid: definite shape and volume Liquid: definite volume but no shape Gas: neither volume or shape Plasma: no volume or shape and the atoms lose electrons and become ions

Explain the Bohr model of the atom

The bohr model says that electrons can only occur in certain specific energy states (quantum levels). The atom gains energy and moves to higher levels and vice versa, the lines on the spectrum correspond to the difference in energy between quantum levels.

What is the Law of Constant Composition?

The compound is broken down into constituent elements, masses of the element will have the same proportions.

Describe why metallic solids are excellent conductors of both electricity and heat.

The delocalized electrons are free to move around at random and therefore they move with the electric current or heat and they make contact with another atom spreading it faster than other bonded compounds.

What accounts for the differences between the properties of ionic and covalent compounds?

The difference between properties of ionic and covalent compounds is that the ionic compounds have a higher strength of attraction which results in a higher melting and boiling point. Covalent compounds are often gas at room temperature and turn to liquid below zero. Ionic compounds are brittle at room temperature due to the alternating charges, and they dissolve in water making them able to conduct electricity while covalent compounds can't.

What does electron configuration describe? What assumption underlies an atom's electron configuration?

The electron configuration describes the arrangement of electrons in space around the nucleus. An atom's electron configuration uses the assumption that electrons are in the ground state.

What can't be determined about the electron using Schrödinger's equation?

The equation cant describe the electron path, the identity when the electron occupies a specific point, and it can't describe how an electron moves.

Identify the two forces that act on atoms as they bond. Explain the origin of these forces.

The forces of attraction and repulsion act on the atoms as they bond. The electrons are attracted to the positive nucleus of the other atom , while the electron shielding repels them at the same time. So it is a push and pull, and once they balanced the bond is formed.

Distinguish between molecular formula and formula units

The formula units are ionic compounds, it is the ratio of an ion present in any size sample of the compounds. The molecular formula shows the types and number of atoms combined in a single molecule.

How are the frequency and energy of electromagnetic radiation related?

The frequency and energy of the electromagnetic radiation are directly proportional.

What are the energy levels represented by the hydrogen emission spectrum called?

The hydrogen emission spectrum energy levels are called principal energy labels, and can be divided into sub levels.

Explain how lone pair and bonding pair electrons are represented in Lewis structures

The lone pair are represented by dots on the Lewis structure, and a bonding pair of electrons are lines that connect the letters of the atoms.

Explain what Bohr learned by studying the emission spectrum of hydrogen atoms.

The model learned that when electrons jump quantum levels they go directly from one level to the next, the idea of the ground state having electrons at a minimum amount of energy. The distance between energy levels decreases as the distance of the energy level from the nucleus increases. They also discovered that electrons circle at fixed distance determined by energy and the further from the nucleus the levels hold more electrons.

Why wasn't the Bohr model of the atom accepted as correct?

The model only explains the spectrum of the hydrogen atom, and neglects the interactions between electrons. It assumes circular orbit for electrons.

Explain the octet rule. Your explanation should include a discussion of the orbitals in the valence shell of the atoms.

The octet rule states that chemical compounds tend to form by gaining, losing, and sharing electrons. The octet of electrons in the highest quantum level.

How does electronegativity relate to chemical bonding?

The power of an atom to attract an electron explains the difference between ionic bonding and polar /non-polar covalent bonding.

What is atomic radius?

The size of an atom is difficult to determine, electron clouds don't have boundaries so it is used to represent size. It is half the distance between the 2 nuclei of identical atoms bonded together.

Why is the periodic table divided into the s,p,d and f blocks? Be able to identify them on the periodic table.

The table is divided into the blocks because of the valence configuration, placement depends on the ending orbital. The is because the qualities of each block is dependent on the element's ability to react.

Explain what occurs during a covalent bond between two chlorine atoms. As part of your explanation, draw electron orbital diagrams and indicate the specific electrons that would be involved in the bond.

The two chlorine atoms have a total of valence electrons would be 14, so with a single bond that shares the electrons between the two 12 electrons would be left over. This would mean that there would be 6 unpaired electrons on each chlorine atom.

How are the wavelength and energy of electromagnetic radiation related?

The wavelength and energy of the electromagnetic radiation are inversely proportional.

How are the wavelength and frequency of electromagnetic radiation related? Explain how we know.

The wavelength and the frequency of an electromagnetic radiation are inversely proportional. As one increases the other will decrease simultaneously for the same amount.

What are polyatomic ions?

These are molecules with a charge, compounds can have shortage or excess of electrons and therefore act as an ion.

Many ionic compounds dissociate in water. What does this mean?

This means that the charges on the water surround an individual ion and pull them away from the lattice. This allows the ion to have the ability to move around and conduct electricity .

What does VSEPR stand for? What assumption is the VSEPR model based on?

VSEPR: Valence Shell Electron Pair Repulsion, it is based on the assumption that the 3D shape of a molecule is based on repulsion of electron regions of the central atoms.

What is wavelength?

Wavelength is the distance between two consecutive peaks measured in a fraction of meters.

Describe what happens to main group elements ionize. In particular, describe what happens to a main group metal and a non-metal as they ionize.

When a main group metal and a nonmetal bond the main group metal loses its electron to the nonmetal causing it to form a positive cation, while the nonmetal that gains the electron will form a negative anion.

Describe what happens to the radius of an atom as it ionizes to become a cation.Then describe what happens to the radius if it ionizes to become an anion.

When an atom ionizes to become a cation it loses an electron, therefore the attraction between the nucleus increases decreasing the radius. When it gains an electron and becomes an anion the added charge will repel each other and cause the radius to increase.

What is a mixture?

material composed of two or more elements or compounds that are physically mixed together but not chemically combined

For groups 1A, be able to name the group, write out their valence configuration and relate that to their general chemical and physical properties.

ns^1, Lithium group excludes Hydrogen, they are highly reactive and can't be found in nature in their pure form, they all ionize to 1+, loss of an electron and they achieve noble gas configuration, they are silvery in appearance and are soft enough to cut, often liquid at room temp.

For groups 7A, be able to name the group, write out their valence configuration and relate that to their general chemical and physical properties.

ns^2 np^5, Fluorine group, they are apart of the p block and is the most reactive group of non-metals, to achieve noble gas they have to gain a single electron, form a single covalent bond with other non-metals, except for At all are diatomic molecules.

For groups 8A, be able to name the group, write out their valence configuration and relate that to their general chemical and physical properties.

ns^2 np^6, Noble Gases, virtually non-reactive, most stable form for elements.

For groups 2A, be able to name the group, write out their valence configuration and relate that to their general chemical and physical properties.

ns^2, Beryllium group, they are less reactive than group 1 but still can't be found in pure form, they all ionize to a 2+, and a loss of two electrons allows for the noble gas configuration.