Question 1

What are moles?

Accepted Answer

A unit for measuring the amount of a substance, since atoms are too small to count normally

(contains  (Avogadro's Number) particles)

Question 2

What is Avagadro's Number?

Accepted Answer

The number of particles (atoms/molecules) in a mole of any substance

(this is constant for every substance; )

Question 3

What is molar mass?

Accepted Answer

The mass of a substance in a single mole of it

Question 4

How do you find the number of moles from the number of particles?

Accepted Answer

Divide the number of particles by Avagadro's Number

Question 5

How do you find the number of particles from the number of moles?

Accepted Answer

Multiply the number of moles by Avagadro's Number

Question 6

How do you find the mass of an element from the number of moles?

Accepted Answer

Find the mass of a single mole of that element (on the periodic table), then multiply that by the number of moles

Question 7

How do you find the number of moles in an element from its mass?

Accepted Answer

Divide the mass by the molar mass of that element (from the periodic table)

Question 8

How do you find the mass of a chemical compound?

Accepted Answer

Multiply the mass of each element by its amount, then add them together

Question 9

How do you do mole equations with compounds instead of elements?

Accepted Answer

First, find the molar mass of the compound, then follow the exact same steps

Question 10

What are isotopes?

Accepted Answer

Types of atoms with the same number of protons (the same element) but different numbers of neutrons

Same atomic number & element type; different atomic mass

Question 11

What is relative abundance?

Accepted Answer

The percentage of an isotope with a specific atomic mass found within naturally occurring samples of an element

( has a relative abundance of 98.90%)

Question 12

What is mass spectrometry?

Accepted Answer

A technique to find the relative abundance of an isotope

Question 13

How do mass spectrometers work?

Accepted Answer

Ionizes atoms and molecules with a high-energy electron beam, then deflects the ions through a magnetic field based on their masses

(technically based on their mass-to-charge (m/z) ratio, not mass, but the charge is usually just 1)

Question 14

What is a mass spectrum of a sample?

Accepted Answer

A graph that shows the relative abundance of ions on the y-axis and their atomic mass on the x-axis

(x-axis is technically the mass-to-charge ratio (m/z), but the charge is usually just 1)

Question 15

How do you find the atomic mass from the relative abundances of isotopes?

Accepted Answer

Multiply the atomic mass of each isotope by its relative abundance, then add them all together

(for chlorine: )

Question 16

How do you recognize an element from its mass spectrum?

Accepted Answer

Find its atomic mass, then see which element is closest to that mass on the periodic table

Question 17

What is the law of constant composition?

Accepted Answer

In any chemical compound, elements always bind in the same proportion with each other

(water is always made of hydrogen and oxygen in a 2:1 ratio)

Question 18

What is the percent composition of a substance?

Accepted Answer

The percent by mass of each element in a compound

(water is 11.11% hydrogen by mass and 88.89% oxygen)

Question 19

What is a compound's empirical formula?

Accepted Answer

The simplest whole-number ratio of atoms in a compound

( and  both have the empirical formula of )

Question 20

What is a compound's molecular formula?

Accepted Answer

A representation of that chemical symbols to indicate elements, and subscripts to indicate the number of atoms

( is the molecular formula for glucose; the lowest ratio of the molecular formula is the empirical formula)

Question 21

How do you find a substance's percent composition?

Accepted Answer

Find the mass of each element in the compound, and divide it by the total mass of the compound

Question 22

How do you find a compound's empirical formula?

Accepted Answer

Start: Assume a 100g sample

Find # of moles: Convert each element from grams into moles, using its atomic mass

Whole number ratio: Divide all the moles by whichever is smallest

Write formula: If all moles are whole numbers, write the moles as the subscript for each element

(if the moles are not whole numbers, you might need to multiply everything by a number)

Question 23

How do you find a compound's molecular formula?

Accepted Answer

Find its empirical formula

Find its atomic mass

Scale the number of atoms per element to match the actual atomic mass to the given atomic mass

Question 24

What is the difference between an element and a compound?

Accepted Answer

An element only consists of a single type of atom ()

A compound consists of multiple types of atoms, linked by covalent or ionic bonds ()

Question 25

What are pure substances?

Accepted Answer

Something that only has a single type of matter

(can be an element or a compound; , , )

Question 26

What are mixtures?

Accepted Answer

Multiple pure substances mixed together

(bonding doesn't occur!)

Question 27

What is the difference between homogenous and heterogeneous mixtures?

Accepted Answer

Homogenous mixtures have a uniform appearance because they are closely mixed (chocolate milk)

Heterogeneous mixtures are not evenly distributed and have multiple components (cereal)

Question 28

What are diatomic elements?

Accepted Answer

Pure elements that form molecules of two bonded atoms

(, , ; Have No Fear Of Ice Cold Beer)

Question 29

What is chromatography?

Accepted Answer

A method for separating solutions through a medium where components move at different rates

Question 30

What is distillation?

Accepted Answer

A method for separating mixtures that are made of liquids

Heats the mixture, which vaporizes the most volatile liquid first, then recondenses it later

Question 31

What is evaporation?

Accepted Answer

A technique to separate a solid from a liquid in a homogenous mixture

The liquid evaporates away, leaving only the solid behind (evaporating water from salt)

Question 32

What is filtration?

Accepted Answer

A separation method to filter mixtures made of particles

Smaller particles pass through the filter, while larger particles get stuck

Question 33

What is magnetic separation?

Accepted Answer

A separation technique that separates magnetic substances from non-magnetic substances using a magnetic

Question 34

What is the Bohr Model?

Accepted Answer

A model of the atom, with a nucleus containing protons/neutrons, and shells containing electrons

Electrons orbit the nucleus in those shells

Question 35

What are electron shells?

Accepted Answer

An orbit around an atom's nucleus, each of which has a different energy level

(closest shell is the 1n shell, second is the 2n shell, etc.)

Question 36

How would an electron change its shell?

Accepted Answer

It would have to absorb/release energy

(absorbing=higher shell; releasing=lower shell)

Question 37

Why are inner shells filled before outer shells?

Accepted Answer

Atoms prefer to have the lowest-energy and most stable configuration

Inner shells have less energy than outer shells

Question 38

What is the valence shell?

Accepted Answer

The outermost shell of an atom, filled with valence electrons

Question 39

What are valence electrons?

Accepted Answer

The outermost electrons in an atom, found in the valence shell

Question 40

What is the octet rule?

Accepted Answer

The tendency of atoms to prefer having eight electrons in their valence shell

(atoms with < 8 valence electrons react to become more stable; )

Question 41

How do you determine the number of valence electrons from the periodic table?

Accepted Answer

Look at the group number, ignoring the transition metals

Question 42

What are core electrons?

Accepted Answer

Electrons that are not valence electrons

(everything not in the outermost shell)

Question 43

What are electron orbitals?

Accepted Answer

Regions of space around the nucleus that specific electrons are usually found in

Electrons don't orbit like planets, and are usually found in more vague patterns

(1s, 2s, 2p 3s, 3p,4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p)

Question 44

What are subshells?

Accepted Answer

Sets of electron orbitals with similar shapes that are found in certain electron shells

(designated by s, p, d, and f; each letter indicates a different shape)

Question 45

What is electronic configuration?

Accepted Answer

A representation of how electrons are arranged in an atom

(oxygen: )

Question 46

What is Coulomb's law?

Accepted Answer

The closer and more charged two forces (like electrons and protons) are, the more attracted they will be to each other

Question 47

What is the photoelectric effect?

Accepted Answer

When electromagnetic radiation (like light) hits a material, it emits electrons

(this is useful in photoelectron spectroscopy)

Question 48

What is photoelectron spectroscopy?

Accepted Answer

A technique that measures the relative energies of electrons in atoms and molecules

We can analyze the spectrum this produces to identify elements

Question 49

How does photoelectron spectroscopy work?

Accepted Answer

A sample is hit with high energy radiation, which causes it to eject electrons (photoelectric effect)

The ejected electrons' kinetic energies are recorded by an energy analyzer

The energy required to eject an electron is known as its ionization energy or binding energy

Question 50

How do you analyze a photoelectron spectroscopy spectrum?

Accepted Answer

Since each peak fills up in order, you can match up each peak to its electron subshell in order

Compare the relative heights to figure out how many electrons are in each

Question 51

What is atomic radius?

Accepted Answer

The distance between an atom's nucleus and its outermost electron

Question 52

What are the trends for atomic radius?

Accepted Answer

Down: increases (more electron shells)

Right: decreases (due to more valence electrons causing stronger attraction)

Question 53

What is electron shielding?

Accepted Answer

Outer electrons are shielded from the attractive protons in the nucleus by the repulsive inner electrons

Question 54

What is ionic radius?

Accepted Answer

The distance from the nucleus to the outermost electron of an ion

Question 55

What is electronegativity?

Accepted Answer

A measure of an atom's tendency to attract shared electrons when it forms a chemical bond

Question 56

What are the trends for electronegativity?

Accepted Answer

Down: decreases (greater atomic radius causes lower electronegativity)

Right: increases (the more electrons in the valence shell, the easier it is to gain another)

Question 57

What is ionization energy?

Accepted Answer

The minimum amount of energy required to remove an electron from an atom or molecule

Question 58

What is first ionization energy?

Accepted Answer

The energy required to remove the loosest electron from an atom or molecule

(each removal is harder than the last, so 2nd ionization energy () > 1st ionization energy ())

Question 59

What are the trends for ionization energy?

Accepted Answer

Down: decreases (due to electron shielding)

Right: increases (valence shell becomes more stable)

Question 60

What is electron affinity?

Accepted Answer

The energy released when an electron is added to the atom to form an anion

(an atom's likelihood of gaining an electron)

Question 61

What is the difference between electron affinity and electronegativity?

Accepted Answer

Electronegativity is the tendency to attract electrons from other elements

Electron affinity is the energy released when an electron is added to an atom

Question 62

What are the trends for electron affinity?

Accepted Answer

Down: decreases (caused by increase in atomic radius)

Right: increases (caused by decrease in atomic radius)

Question 63

What is effective nuclear charge ()?

Accepted Answer

The net positive charge valence electrons experience

(increase in atomic number (# protons) causes this to go up; increase in shielding electrons causes this to go down)

Question 64

How do you calculate effective nuclear charge?

Accepted Answer

(Effective nuclear charge) = (atomic number) - (# of shielding electrons)

Unit 1: Atomic Structures & Properties, AP Chemistry Flashcards