chapter 4

Question 1

nucleons

Answer 1

protons and neutrons (in the nucleus)

*pg 50

Question 2

atomic number(Z)

Answer 2

the number of protons in the nucleus of an atom. it determines what element the atom is.
This is written on the bottom left of an element

Question 3

the mass of a proton,electron and neuron

Answer 3

protons and neutrons have a mass slightly more than 1 amu (1 amu = 1.66x10^-27 kg)
electrons has a mass that is about 0.05 percent the mass of either a proton or neutron
-this is why majority of the mass of an atom is due to the nucleus
*pg50

Question 4

atom’s mass number, A

Answer 4

the number of protons plus the number of neutrons
A = Z + N
this is written on the left top of an element, and can also be written after the name (ex: beryllium-9)
*pg50

Question 5

isotopes

Answer 5

two atoms of the same element that differ in their number if neutrons. they always have the same atomic number but different mass numbers
*pg51

Question 6

atomic weight of an element

Answer 6

is a weighted average of the masses of its naturally occurring isotopes.
*pg51

Question 7

how is the atomic weight of an element calculated

Answer 7

you check how much each isotope accounts for and multiply the percentage by the atomic mass of that isotope. do this with all the isotopes and add all the answers in the end
*pg51

Question 8

ions

Answer 8

when a neutral atom gains or looses electrons it becomes charged, and therefore an ion.
anions are negatively charged ions and cations and positively charged
this charge goes on the top right of the element
*pg52

Question 9

strong nuclear force

Answer 9

the force through which protons and neutrons are held together in the nucleus. it’s stronger than the electrical force between charged particles. this force is the most powerful but only works at extremely short distances
*pg53

Question 10

radioactive nuclei

Answer 10

these are unstable nuclei, and they undergo a transformation to make them more stable.
*pg53

Question 11

radioactive decay

Answer 11

the process of making a radioactive nuclei more stable, it works by altering the number and ratio of protons and neutrons or just lowering their energy. there are 3 types: alpha, beta, and gamma. the nucleus that goes through this process is known as the parent, and the resulting more stable nucleus is known as the daughter
*pg53

Question 12

alpha decay

Answer 12

when a large nucleus wants to become more stable by reducing the number of protons and neutrons, it emits an alpha particle. (α with a 4 in the top left and 2 in bottom left, meaning it consists of 2 protons and 2 neutrons). this is equivalent to a helium-4 so it can also be denoted by He with the same subscripts as the alpha.
alpha decay reduces the parent’s atomic number by 2 and the mass number by 4.
although alpha particles are emitted with high energy from the parent nucleus, this energy is quickly lost bc it travels through matter or air. as a result it cannot travel far, and can be stopped by the outer layers of human skin or piece of paper
*pg53

Question 13

beta decay

Answer 13

three types: β−, β+, and electron capture
each of these involves the conversion of a neutron into a proton, or vice versa, through the action of weak nuclear force
beta particles are more dangerous than alpha particles bc they beta particles are much smaller so they have more energy and a greater penetrating ability, but they still can be stopped by an aluminum foil or a cm of plastic or glass
*pg54

Question 14

β− decay

Answer 14

when an unstable nucleus contains too many neutrons, it may convert a neutron into a proton and an electron (which is known as β− particle), which is ejected.
the atomic number of the resulting daughter nucleus is 1 greater than the radioactive parent nucleus, but the mass number remains the same.
ex: Carbon-14 would become Nitrogen-14
this one is the most common type of beta decay (if it just says beta decay on a question without referring to an exact one, it means β−)
*pg54

Question 15

β+ decay

Answer 15

Also known as positron emission
when an unstable nucleus contains too few neutrons, it converts a proton into a neutron and a positron, which is ejected.
this positron is the electron’s antiparticle, it’s identical to an electron except its charge is positive.
the atomic number of the resulting daughter nucleus is 1 less than the parent but the mass number remains the same.
EX: Fluorine-18 would become oxygen-18

Question 16

electron capture

Answer 16

a way for an unstable nucleus to increase its number of neutrons by capturing an electron from the closest electron shell (the n=1 shell) and use it in the conversion of a proton into a neutron.
this is similar to the β+ in the case that it casues the atomic number to reduce by 1 while the mass number stays the same.
EX: Chromium-51 + electron –> vanadium-51
*pg55

Question 17

Gamma decay

Answer 17

a nucleus in an excited energy state (usually after going through alpha or any beta decay) can ‘relax’ to its ground state by emitting energy in the form of one or more photons of electromagnetic radiation.
These photons are called gamma photons/rays (γ). they have a very high frequency and energy. they have neither mass nor charge, and can therefore penetrate matter most effectively. a few inches of lead or about a meter of concrete will stop gamma rays.
their ejection changes neither the atomic number or the mass number.
EX: Silicon-31 going thu B- –> Phosphorus-31 (excited state) -going through gamma decay –> P-31
basically this decay does not change the identity it is simply an expulsion of energy
*pg55

Question 18

Half life

Answer 18

different radioactive nuclei decay at different rates. the half life is the amount of time it takes for one half of some sample to decay
denoted by t1/2.
the shorter the half life the faster the decay. it decreases exponentially
1 half life= 50% remaining; 2 half-lives = 25%remaining; 3 half-lives = 12.5%; 4 half lives = 6.25%
equation: N = N0 (1/2)^(T/t1/2) or N = N0e^(-kt)
T = the time elapsed; k = decay constant (k= ln(2)/t1/2).
The shorter the half life the greater the decay constant
*pg58

Question 19

nuclear binding energy

Answer 19

every nucleus that contains both protons and neutrons has a nuclear binding energy
This is the energy that was released when the individuals nucleons (protons and neutrons) were bound together by the strong force to form the nucleus. it’s also equal to the energy that would be required to break up the intact nucleus into its individuals nucleons. the greater the binding energy per nucleon, the more stable the nucleus.
The greater the binding energy per nucleon, the more stable the nucleus.
*pg60

Question 20

what happens when the nucleons bind together to form the nucleus

Answer 20

some mass is converted to energy, so the mass of the combined nucleus is less than the sum of the masses of all its nucleons individually.
*pg60

Question 21

Mass defect

Answer 21

symbol: Δm
The difference bw the mass of the combined nucleus and mass of separate nucleons.
It’s energy is equivalent is the nuclear binding energy.
For a stable nucleus the mass defect = (total mass of separate nucleons) - (mass of nucleus) will always be positive
*pg60

Question 22

Einstein’s equations for mass-energy equivalence

Answer 22

E_b = (Δm)c^2
c = speed of light = 3x10^8 m/s.
Masses can be in Kg and energy in Joules (1 Kg 9x10^16 J)
In the nuclear domain though, masses are often expressed in amu (1 amu = 1.66x10^-27 Kg) and energy in electronvolts (1 eV = 1.6x10^-19 J). so:
E_b (in eV) = [Δm(in amu)] x 931.5 MeV
*pg61

Question 23

emission spectrum

Answer 23

the light emitted by an element in its gaseous form when electric current is passed through, put through a prism and have its light separated into its components wavelengths.
An atom’s emission spectrum gives an energetic “fingerprint” of that element because it consists of a unique sequence of bright lines that correspond to specific wavelengths and energies. The energies of the photons, or particles of light that are emitted, are related to their frequencies, f, and wavelengths, λ by the equation:
E_photon = hf = h c/λ
h = Planck’s constnt (6.63 x 10^-34 Jxs)
*pg 61-62

Question 24

what did Bohr propose in his new model

Answer 24

He said that the electrons in an atom orbitted the nucleus in circular paths, like the planets orbit the sun. The distance from the nucleus was related to the energy of the electrons; the greater their energy the farther they were from the nucleus. He also said there were quantized energy states around the nucleus and electrons could only be on one of them (n = 1, 2, 3 ,4, 1 being the closest to the nucleus)
*pg62

Question 25

what happens when the electrons absorb or lose energy

Answer 25

if electrons absorb energy that’s exactly euqal to the difference in energy between its current level and that of an available higher lever, it “jumps” to that higher level
if electrons lose energy they “drop” to a lower energy level, emitting a photon with an energy exactly equal to the differences between the levels.
Electrons can gain or lose very specific amounts of energy bc of the quantized nature, which is why only photons with certain energies are observed which correspond to very specific wavelengths
*pg62

Question 26

what did Bohr’s model predict

Answer 26

It predicted that elements would have line spectra instead of continuous spectra (which would be the case if transitions bw all energies could be expected)
*pg62

Question 27

electron energy absorption vs emission

Answer 27

Absorption:
(+ energy change)
Electron is at ground state on n = 1 (lowest possible energy level). incoming photon is absorbed by E1 and it jumps to E2 (electron jumps to higher level)

Emission
( - energy change)
Electron is in an excited state on n = 3. Electron emits photon and drops from E3 to E2 (Electron drops to lower energy level)
*pg63

Question 28

Electron from excited state to ground state

Answer 28

Electrons excited to high energy can’t relax to ground state in large jumps so they relax in a series of smaller jumps (thus why it goes to E2 from E3 instead of E1)
when the electron jumps to n = 2 we expect to detect a photon with energy with a longer distance
When the electron jumps straight down to n=1, we expect to detect a more energetic photon of energy corresponding to the difference bw n=3 to n=1 (shorter distance)
*pg63

Question 29

formula for calculating the energies of the discrete levels of the bohr model

Answer 29

E_n = (-2.178e-18J) / n^2
the difference bw energies of the two possible photons can be calculated by:
ΔE_n = E_n3 - E_n2
For electrons falling from excited state will be negative, and ones that are jumping up from ground will be positive
*pg63

Question 30

wavelength calculation from energies:

Answer 30

ΔE = h c/λ
(not all electron transitions prod photons we can see with the naked eye, but all transitions in an atom will produce photons either in the ultraviolet, violet, or infrared region of the electromagnetic spectrum)
*pg63

Question 31

Bohr atom

Answer 31

bohr atom is one that contains only one electron

*pg64

Question 32

what was the point of the quantum model of the atom

Answer 32

The Bohr model does not predict the atomic spectra of many-electron atoms (it only does one-electron atoms), bc of that it can’t describe electron-electron interactions that exist in many-electron atoms so the quantum model was developed to account for these differences.
*pg65

Question 33

The energy shell in a quantum model

Answer 33

symbolized n. The energy shell of an electron in the quantum model of the atom is analogous(comparable) to the circular orbits in the Bohr model of the atom. An electron in a higher shell has a greater amount of energy and a greater avg distance from the nucleus.
*pg65

Question 34

orbital

Answer 34

a three dimensional region around the nucleus in which the electron is most likely to be found
*pg66

Question 35

The energy subshell

Answer 35

In a quantum model. it’s comprised of one or more orbitals, and is denoted by a letter (s,p,d, or f) that describes the shape and energy of the orbital(s). they get more complex as they go higher in energy in the order listed. Each energy shell has one or more subshells, and each higher energy shell contains one additional subshell.
EX: the first energy shell has s and the second energy contains both s and p, and so on
*pg66

Question 36

The orbital Orientation

Answer 36

Each subshell contains one or more orbitals of the same energy (also called degenerate orbitals), and these orbitals have different 3d orientations in space. the number of orientation increases by 2 in each successive subshell.
EX: the s subshell contains one orientation and the p subshell contains 3 orientations
Each S subshell has just one spherically symmetrical orbital (can carry 2 e) , each P subshell has 3 orbitals (cam carry 6 e) (in a dumbbell shape) p_x, p_y, p_z orbital
*pg66

Question 37

The electron spin

Answer 37

Every electron has 2 possible spin states, which can be considered the electron’s intrinsic magnetism. Because of this every orbital can accomodate a max of 2 electrons, one spin-up and one spin-down. if an orbital is full, we say that the electrons it holds are “spin-paired”
*pg67

Question 38

Electron configuration rules

Answer 38

1) Electrons occupy the lowest energy orbitals available, they are filled in order of increasing energy (Aufbau principle)
2) Electrons in the same subshell occupy available orbitals singly, before pairing up (Hund’s rule)
3) There can be no more than 2 electrons in any given orbital (Pauli Exclusion principle)
* pg 67

Question 39

Electrons per subshell

Answer 39

s = 2 
p = 6
d =10
f = 14
*pg69

Question 40

Noble gases and electron configuration

Answer 40

Noble gases always have their subshells filled. (the lone exception is Helium). this means they have a complete octet, which remarks for their chemical stability and lack of reactivity
*pg69

Question 41

Diamagnetic atoms

Answer 41

an atom that has all of its electrons spin-paired
EX: helium, Beryllium, and neon
It must contain an even number of electrons and have all of its occupied subshells filled. Because all the spins are paired the individual magnetic fields they create are cancelled, leaving no magnetic field. these atoms are repelled by an externally produced magnetic field
*pg69

Question 42

Paramagnetic atoms

Answer 42

when an atom’s electrons are not all spin-paired. these are attracted unto externally produced magnetic fields.
*pg70

Question 43

A period in periodic table

Answer 43

each horizontal row

*pg 71

Question 44

A group/family in a periodic table

Answer 44

Each vertical column. within each group all the elements have the same number of electrons in the outermost shell

Question 45

Blocks in periodic table and what do they indicate

Answer 45

S block is group 1-2 (starting at H and ending at Be)
P block is group 3-8 (starting at B and ending at He)
D block is all the groups in the middle of s and p
F block is the lanthanide and actinide series on the bottom (the 2 periods at the bottom)
They indicate the highest energy subshell containing electrons in the ground-state of an atom within that block. (EX: C is in the p block and its config is 1s^2 2S^2 2p^2)
*pg71

Question 46

Things to remember when using the blocks to write configuration

Answer 46

• whenever you’re in the d block, subtract 1 from the period number
• whenever you’re in the f block, subtract 2 from the period number
• check more on pg72

Question 47

elements that are Exceptions to the normal configuration rule

Answer 47

Chromium’s normal config would be [Ar]4s^2 3d^4, but Cr is known to be more stable when it’s d shell is half-filled so the s subshell gives up one of its electrons to d and it becomes [Ar]4s^1 3d^5. other elements that follow the same rule are:
Cu, Mo (same family as Cr), Ag and Au (both in the same family as Cu)
*pg73

Question 48

Electron configurations of anions and cations

Answer 48

Anions:
– when an electron is gained, they go in the first available orbital (the one with the lowest available energy)
– we move to the right of the periodic table the same number as the number of electrons gained
– for Ex: F- will have an extra electron in the p subshell (will have the same config as Neon)
Cation:
– when an electron is lost, we take out an electron from the lowest energy
– we move to the left
*pg73

Question 49

Isoelectronic

Answer 49

When 2 elements have the same configuration due to one of them being an ion
EX: F- and Ne
*pg73

Question 50

Transition metals getting ionized

Answer 50

Transition metals are all in the d block
when they are ionized they always lose s electrons before they lose d electrons (even though normally the electrons on the highest n level get lose first which should be d)
EX: Ti has a config of [Ar]4s^2 3d^2 but for Ti+ it will be [Ar]4s^1 3d^2, and for Ti2+ it is [Ar]3d^2
*pg74

Question 51

configurations in excited state

Answer 51

Excited state is when its an abnormal configuration like having 2d, or not having any more than 2e- per orbital, or having more than possible in a subshell, etc.
*pg75

Question 52

Valence electrons

Answer 52

Electrons in the atom’s outermost shell. These are primarily responsible for an element’s properties and chemical behaviour.
*pg76

Question 53

some groups/families that have special names (and their valence-shell configurations)

Answer 53

Group I: Alkalai metals. ns^1
Group II: Alkaline Earth Metals. ns^2
Group VII: Halogens. ns^2np^5
Group VIII: Noble gases. ns^2np^6
the d block: transition metals
the s and p blocks: representative elements
the f block: Rare Earth metals
*pg76

Question 54

A closed-shell (fully-filled valence shell)’s properties

Answer 54

These are mostly noble gases, this configuration is called an octet. these result in great stability (and therefore low reactivity). This is why noble gases don’t normally undergo chemical reactions, so most group VIII elements are inert (including He, even though its not an octet)
*pg76

Question 55

Behavior of Alkali and Alkaline Earth metals

Answer 55

They behave as reducing agents (i.e lose valence electrons) in redox reactions to get a stable octet, generally as M+ or M2+ cations.
*pg76

Question 56

Behaviour of Halogens

Answer 56

They require a single electron to achieve a stable octet. they exist as diatomic molecules (e.g F2), where one electron from each atom is shared in a covalent bond. When combined with other elements they act as powerful oxidizing agents (gain electrons), they can become stable as either X- anions or by sharing electrons with other nonmetals.
*pg76

Question 57

Reactions bw elements on opposite sides of the periodic table

Answer 57

These reactions are quite violent. This occurs due to the great degree of stability gained for both elements when the valence electrons are transferred from the metal to the nonmetal.
*pg76

Question 58

Metalloids

Answer 58

Elements that possess qualities of both metals and nonmetals. These elements are: B, Si, Ge, As, Sb, Te, Po
*pg77

Question 59

Nuclear shielding / shielding effect

Answer 59

Each filled shell between the nucleus and the valence electrons shields (‘protects’) the valence electrons from the full effect of the positively charged protons in the nucleus. The electrical pull by the protons in the nucleus reduced by the negative charged of the electrons in the filled shells in between. The result is an effective reduction in the positive elementary charge.
*pg78

Question 60

Atomic radius in the periodic table

Answer 60

As we move across the periodic table, the electrons increase but the shells do not (they are only initiates at the beginning of the period), which means the valence electrons are more tightly bound to the atom bc they feel a greater effective nuclear charge. so as we move across the periodic table from left to right, the atomic radium decreases.
But down a group, theres new shells being added at every period so valence electrons are less tightly bound since they feel a smaller effective nuclear charge. so atomic radius increases when going down a periodic table due to their increases shielding
*pg78

Question 61

Atom’s (first) ionization energy (IE or IE1)

Answer 61

The energy it takes to remove the least tightly bound electron from an isolated atom. As we go left to right across a period, or up a group, the ionization energy increases since the valence electrons are more tightly bound.
*pg79

Question 62

Atom’s second Ionization energy (IE2)

Answer 62

The energy it takes to remove the least tightly bound electron from the cation X+. IE2 is always greater than IE1
*pg79

Question 63

Electron affinity (EA)

Answer 63

The energy associated with the addition of an electron to an isolated atom is known as the atom’s electron affinity. If energy is released when the electron is added the EA will be neg and positive if its required. halogens have large negative EA. Noble gases and Alkaline earth metals have positive EA because they get destabilized
EA typically becomes more negative as we move to the right across a row or up a group (noble gases excepted), but there are anomalies in this trend
*pg79

Question 64

Electronegativity

Answer 64

measure of an atom’s ability to pull electrons to itself when it forms a covalent bond. A measure of how much an atom will “hog” the electrons that its sharing with another atom. the greater the tendency to attract the greater the electronegativity. It increases as we move from left to right across a period, and decreases as we go down a group (similar to ionization energy). some common:
F>O>N ≈ Cl > Br > I > S >C ≈ H
*pg79

Question 65

Acidity

Answer 65

a measure of how well a compound donates protons, accepts protons, accepts electron, or lowers pH in a chemical system. It increases from left to right across a period(because the more electronegative the more stable an element is) and increases as we go down a group (the larger the anions the more the negative can be delocalized and stabilized)
*pg79/80

Question 66

A binary Acid

Answer 66

has the structure HX, and can dissociate in water like: HX –> H+ + X-
stronger acids have resulting X- anions that are likely to separate from H+ bc they are stable once they do.
*pg79