Chem Review Flashcards
1
Q
Elemental Composition of Human Body
A
Hydrogen= 63% Oxygen= 24.2% Carbon= 10.5% Nitrogen=1.35% Major Minerals=0.7% Trace Elements= 0.01%
2
Q
Dalton’s Theory of the Atom
A
All matter is composed of atoms that can be neither created nor destroyed.
Atoms of a particular element are identical in size, shape, mass and all other properties and differ from atoms of other elements in these properties.
3
Q
Atom
A
Element in its smallest form
4
Q
Molecule
A
Two or more atoms combined (bound)
The atoms may be same element or different elements
5
Q
Atomic weight
A
Similar to mass
Relative masses of atoms are related to the most abundant carbon isotope, Carbon 12, and differ widely in masses.
6
Q
Why is the weight of carbon listed as slightly higher than 12 sometimes?
A
Because of the existence of some carbon isotopes in nature, Carbon 13 for example
7
Q
Neutron
A
No charge (0) Amu= 1.0087
8
Q
Proton
A
Positive Charge +
Amu=1.0078
9
Q
Electrons
A
Negative charge -
Amu= .00055
10
Q
Most distinguishing characteristic of an element?
A
The number of protons, or positively charged particles in the nucleus of an atom.
If you lose a proton, you will have a different element
11
Q
Mass of an element is composed of?
A
Protons and neutrons
Electrons are very small are hardly contribute to the mass (atomic weight)
12
Q
Atomic Nucleus
A
Atoms have a small concentrated positive charge in the atomic nucleus
13
Q
What occupies the surrounding space around the nuclear atom?
A
Most of the atom is space and electrons occupy this surrounding space.
Nucleus has a positive charge and electrons has a negative charge and these will be attracted to each other
14
Q
How much space do electrons and protons take up in atom?
A
Nucleus takes up a very small amount of the atom=protons
Electrons circulation around the nucleus take up the most space
15
Q
The Neutral Atom
A
Number of electrons=number of protons
16
Q
Z number of an element
A
Represents Atomic number
Number of protons
If element is neutral, then protons and electrons are equal
17
Q
How are atoms presented on the periodic table?
A
In their neutral form, although they are not neutral in the environment. This is just an easier way to study them
18
Q
Can two elements ever have the same number of protons?
A
NO, that’s the distinguishing factor
19
Q
In the periodic table how are elements arranged?
A
According to atomic number
20
Q
General notation of elements. What does A, E and Z represent?
A
A= mass (protons+neutrons)
E=element by identity symbol
Z=atomic number (number of protons)
21
Q
As we move down the periodic table what do we see?
As we move across what do we see?
A
We see similar properties of elements in columns as we move down
We see different properties as we move across?
22
Q
Isotopes
A
Some atomic masses differ for same atom
Isotopes that have the same atomic number, but different atomic masses.
In isotopes, the atomic nucleus of a given element has a fixed number of protons, but the neutrons vary
Not all isotopes are radioactive
23
Q
Hydrogen vs. Deuterium (2H)?
A
Hydrogen has 1 proton and 0 neutrons= atomic mass of 1
Deuterium has 1 proton and 1 neutron= atomic mass of 2
24
Q
Inert or noble gases properties
A
VIIIA (far right of periodic table)
Helium, Argon, Krypton, Xenon, Radon
Properties: do not react, all gases at normal temperature
25
Alkali or light metals
IA, except H- Far left of table
Lithium, Sodium, Potassium, Rubidium, Cesium, Francium
Properties: in pure form have shiny lust, good conduction of heat and electricity
26
Halogens
Group VII A
Fluorine, Chlorine, Bromine, Idoine
Properties: no metals, poor conductors of heat and electricity, all react with hydrogen to form hydrogen halide. Ex: hydrogen fluoride, hydrogen chloride
27
Transition Metals
IIIB-IIB can have variable charges
Row 3 of table- Magnesium, Sulfur.
A decrease in metallic properties is seen.
28
Atomic Radii of elements
Increase in atomic radii from top to bottom of periodic table
29
The effect of ionization in atomic radii
The addition of electrons has a major effect on atomic size
| The addition or removal of a single electron roughly increases or decrease the radii by half.
30
Ionized
Gaining or losing an electron
31
Electronegativity
The ability of an atom to draw (attract) electrons or a negative charge towards it.
Electronegativity is not ionization.
Values are relative, note that fluorine has the highest value of 4.0
Electronegativity increases left to right, and decreases from top to bottom.
32
Why do elements at the bottom of the periodic table has decreased Electronegativity?
When a neutral atom has more protons, it has more electrons.
Electrons shield that nucleus and have less interaction with the protons.
More electrons=more shielding=less Electronegativity
33
Ionization
Energy required to ionize an element
Inert elements have the highest ionization energies-- most difficult to ionize
Easiest to ionize= Li, Na, K, Rb, Cs
34
Nuclear Stability
Nucleus is packed tightly with positive particles and would seem to want to fly apart
Neutrals act to stabilize the nucleus
In order to achieve stability, the more protons in a nucleus- there needs to be more neutrons.
35
Ionization energy is a periodic property of elements
Which elements hard to ionize?
Which elements easier to ionize?
Hard to ionize or require the most energy to ionize is Helium.
Inert elements are hard to ionize, they have 8 electrons in outer shell and do not like to lose this electron
Easiest to ionize= Alkali metals, Lithium, Sodium, Potassium
Usually give up on electron and become positively charged
36
When the neutron-to-proton ratio is too high or too low what happens?
Too high or too low= nuclear stability is altered leading to radioactive processes.
37
Radioactive processes
Occurs when nuclei are trying to achieve stability
This process changes the number of neutrons or protons to try to reach stability.
When this occurs they release energy in a form of radioactive particles
38
Beta particle
An electron, or -1 charge that is released during radioactive decay process
39
Alpha particle
Associated w/ heavier elements normally
| Alpha particle= two protons and two neutrons (+2 charge)
40
Gamma rays
(Y)= no mass or charge, but high energy particles (photons)
41
When radioactive decay occurs does the element change?
YES
| Sometimes number of protons is changed. Example: tritium in notes
42
As elements get larger, what happens to neutron-to-proton ratio?
As element gets larger, they are less stable because there are more protons, and nucleus gets bigger. It then is harder to hold this element together.
Neutrons are thought to play a role in stabilizing the protons and keeping them together
43
Carbon14
Is an isotope that is used for carbon dating
1/2 life of carbon 14=5670 years
Half life is the time it takes for radioactivity intensity to decrease by half. You can use this number of determine the age of organic materials
Less carbon 14=older the element is
44
Gamma rays penetration
Gamma rays completely penetrate through the body, most worrisome than alpha and beta.
Any exposure to alpha, beta or gamma is related to HOW MUCH you are exposed to
45
What determines an electrons reactivity?
The electrons in atoms
46
Neil's Bohr
Proposed that only specific energy levels are possible for electrons in atoms
-electrons circle the nucleus only in certain allowed orbits of specific radii
47
Quantum Mechanics
Fixed amount- related to how many electrons can fit in an orbit
48
The energy levels are identified by number. Electron population is determined by what equation?
2n(2)
| N=energy level, the principal quantum number
49
Energy level of electrons in an atom
As N increases, the electrons spend more time farther from the nucleus and are less tightly bound to the nucleus.
Lower energy levels- more stable the atom is
50
In the first energy level, the electrons nearest the nucleus have the highest or lowest energy level?
These electrons have the lowest energy level, but they are tightly attracted*
51
As we move up energy level, i.e. From n=1 to n=2, electrons what happens to energy?
As you move up energy levels- you are farther from nucleus, these electrons are less attracted to the nucleus but have more energy. These are less stable electrons.
52
```
Maximum electron population of each energy level
N=1
N=2
N=3
N=4
```
N=1, 2(1) squared= 2 electrons
N=2, 2(2)squared=8 electrons
N=3 2(3)squared=18 electrons
N=4 2(4)squared=32 electrons
53
Electron Shells (energy levels)
Shells or energy levels are composed of subshells, which are composed of orbital.
Shells(energy level or orbitals)>subshells>orbits
Start at:
1(K)
2(L)
3(M)
4(N)
54
Which electrons confer reactivity?
KEY POINT: electrons in the outer shell confer reactivity
55
Stability of an element is most closely related to what number?
8 is the magic number for stability.
Inert gases have 8 electrons in their outer shell=stable
Most elements want 8 in their outer shell to be stable.
56
Shells- subshells- orbitals
Energy level or shells= 1 (K), 2 (L), 3 (M), 4 (N)
Subshells= s, p, d, f
Orbitals= 1, 2, 3
57
S subshell (number of electrons and orbitals)
S subshell= 2 electrons total, spherical shaped orbital
| one S orbital per energy level
58
P Subshell (number of electrons and number of orbitals)
P subshell= 6 electrons, 3 p orbitals per energy level (each orbital can have a maximum of 2 electrons, for a total of 6)
Orbitals exist along different axes: X, y, z
Dumbbell shape
59
D subshell (number of electrons and orbitals)
D subshell=10 electrons, five D orbitals exist in energy levels above N=2. (Each orbital can hold a max of 2 electrons for a total of 10 electrons in the d subshell)
Four leaf clover shape
60
F subshell (number of electrons and orbitals)
F subshell=14 electrons, 7 orbitals above n=3. Each orbital can hold a max of 2 electrons for a total of 14 electrons.
Complicated shape.
61
Electron probability distribution
It is not ever possible to determine exactly where electrons are around the nucleus. Electrons in orbitals are not defined locations, but are distributed based on probabilities of location.
As you move away from the nucleus, electron probably is much lower
62
1s electron density distribution
Electron density distribution, such as Hydrogen atom, in the ground state makes a spherical shape of distribution.
63
2p electron density distribution
Electron density distribution is a dumbbell shape. 2 electrons are circulating in a figure 8 manner
64
Two electrons in an orbital have similar or opposite signs?
Two electrons in an orbital have opposite spins or opposite signs because they want to pair up
65
What happens to the filling of shells as you move up higher energy levels?
Sometimes the filling of shells is NOT sequential, meaning you can fill the 4th energy level before we fill the 3rd energy level.
66
Why does the atomic radii decrease in the center part of periodic table, i.e. Transition metals?
The electrons in the transition metals live more happily close together, making the atomic radii smaller.
67
Reactivity of electrons in atoms
Electrons in the lowest energy level require the most energy to be removed from the atom.
Electrons in the higher energy level require the LEAST energy to be removed from the atom
68
What atoms are most likely going to be involved in chemical reactions?
The highest energy level electrons (those in the outer shell).
Not as tightly attracted to nucleus because they're farther away from the + charge
69
Valence Electrons- Lewis Diagram
The dots represent the electrons in the outer shells
| These outer electrons are responsible for the valence, or combing capacity of atoms
70
Valence Electrons
Electrons that belong to a a valence shell
71
Valence Shell
The outermost shell of an atom
72
Valence
Number of bonds an atom can form
73
Saturation of Valence
There is a limit to combining ability of one atom to another
Related to the number of electrons that are in the outer shell that can shared or bound
Example: Carbon can form only 4 bonds- no more no less, trying to achieve 8 electrons in outer shell for stability
74
Rule of Eight, or Octet Rule
Bonds are formed such that each atom is surrounded by a complete Octet (8) of electrons (except hydrogen)
The molecule is more stable with 8 electrons in the outer shell of its atom whether it shares them or not
75
Orbital Notations- Hydrogen
One electron in outer shell=
| 1s(1)
76
Orbital notation for carbon
Carbon= 1s(2) 2s(2) 2p(2)
OR
Promotion allows four bonds to form
1s(2) 2s(1) 2px(1) 2py(1) 2pz(1) (shows that there is 4 bonds available for sharing
77
Orbital Notation for Nitrogen
1s(2) 2s(2) 2p(3)
OR
1s(2) 2s(2) 2py(1) 2px(1) 2pz(1)
78
Hydroxyl Group
O-H
79
Carbonyl or Keto Group
Carbon double bonded to oxygen=4 bonds are shared
80
Ene suffix
Aminated alkene
| Double bond
81
Amine
N-H
82
Atoms are more stable when their outer shells are filled... They can do this in two ways?
1. Ionization
| 2. Electron Sharing
83
Ionization or sharing of elements leads to ______________
Bonding with other atoms to form molecules
84
Ionic Bonds
Atoms can fill their outer shells by completely acquiring or losing electrons and in doing so become ionized
The consequent electrostatic (+ attraction to a -)interactions result in ionic bonding
Valence electrons are NOT shared
85
Example of sodium and chloride as an ionic bond
(Na) will lose an outer electron to form a cation {a cation is positively charged atom or molecule)
(Cl-- which is a halogen) will gain an electron to form an anion {an anion is negatively charged atom or molecule}
Idea= atoms w/ opposite charge have the largest attraction
86
A few examples of ionic compounds
LiF- lithium fluoride
NaF- sodium fluoride
NaBr sodium bromide
NaI- sodium iodide
- These are strongly attracted to each
- Note that these ionic compounds (salts) contain the IA alkali metals and the halogens (7A)
- These are strongly bound atoms requiring high energy to separate into free ions. They dissolve in water
87
What exactly does stability represent?
When atoms achieve stability they have 8 electrons in their outer shell, meaning they can exist and have a longer lifetime
88
Covalent Bond
In covalent bonds, electrons are shared between atoms
89
Example of covalent bond: H2
- The sharing of two electrons (a pair) between atoms results in a SINGLE bond or sigma bond.
- Single bond between two atoms is sausage shaped
- we generally don't find pure hydrogen in nature very much
90
Electronegativity
Ability of an electron to attract electrons to it
91
Covalent bond example: Chlorine
Neutral chlorine has 7 electrons in its outer shell, i.e. 7 valence electrons
-- it has single vacancy in the 3p i.e. 1s(2) 2s(2) 2p(6) 3s(2) 3p(5)
orbital that can be filled by sharing another single electron (a single bond)
- chloride gas is relatively stable but not too stable
92
Example of covalent bond: Carbon and Hydrogen
Carbon has four valence electrons
Hydrogen has 1 valence electron
Carbon possesses an octet when bound to four other atoms (covalent bond)
93
Examples of common covalent bonds
```
C-C
O-H
C-N
C-O
Cl-Cl
```
- These can only contain sigma bonds, but those capable may contain multiple bonds.
- Bonds drawn as a single line represent the sharing of two electrons
94
Covalent and Ionic Bonding: Nitrogen and Hydron
Nitrogen has 5 valence electrons
When bound to 3 hydrogens it has an octet
However one pair of its electrons is unbound in the octet
The unbound pair of electrons can associate (bind) with a cation such as a proton and the molecule becomes uncharged.
95
Ionic Bonds:
Ionic bonds- electrons are transferred
NaCl
Do NOT share electrons
96
Polar Covalent Bonds
Electrons are unequally shared
| HCl
97
Covalent Bonds
Electrons are shared equally
| H-H
98
Dipole
A molecule with on end having a slightly (partial) negative charge and the other end having a slight positive charge (NOT ionic bonds)
99
Atoms can share more than one pair of electrons resulting in more than one bond between atoms....
Single bond vs Double bond vs Triple bond
Single bond= one sigma bond- saturated compound
Double bond= one sigma bond + 1 pi (p) bond
Triple bond= one sigma bond + 2 pi bonds
100
Ethane
Single bond
101
EthEne or ethylene
Double Bond
102
Ethane (or acetylene)
Triple bond
103
Aromatics
Alternating double bonds in a ring system
104
When pi electrons (from overlapping p orbitals) delocalize around the ring and make the ring _________
More stable, i.e. The pie electrons are in a lower energy state
105
Molecular Nitrogen Formula
N2- in atmosphere inert gas common, abundant gas
Molecular nitrogen shares 3 pairs of electrons, therefore it contains a triple bond. One s bond and 2 p bonds
106
Nitrogen Facts
Odorless gas, does not support combustion
melting point= -210 degrees C
Boiling point= 196 C
107
Breakdown of the Octet Rule (NO)
Nitrogen Oxide (Nitric Oxide)- neutral, but reactive, used as a vasodilator gas
