Atomics Structure & Periodic Trends Flashcards
What is a molecule?
When two or more atoms join together
What is a compound?
A molecule composed of multiple different elements
Protons
Carry a positive charge (approx. 1.6 x 10-19 coulombs (C)) = elementary charge (e) 1 atomic mass unit (amu) or 1 Da A nucleon (b/c resides at the nucleus of an atom)
Neutrons
Slightly more than 1 amu, but we estimate as 1 amu
A nucleon
Electrons
Super small, mass negligible
-1.6 x 10-19 C, so the reverse sign but same magnitude as a proton
Held close to nucleus but not nucleons
Exist in electron cloud around nucleus of an atom
Atomic Number
Termed Z
The same as the number of protons in an atom
Gives an atom it’s identity
Mass Number
Termed A
Total of neutrons and protons in a nucleus
How are atomic and mass numbers typically represented for an element?
Mass number is on top, atomic on bottom
What are the common isotopes of Hydrogen? What form are we most familiar with?
Common = Protium
Isotopes = Deuterium (mass = 2), Tritium (mass=3)
Deuterium will be labeled D if it’s a hydrogen that has been weighted for tracking in a reaction
Difference between Atomic Weight and Atomic Mass
Atomic weight = average of all different isotopes of an element
Atomic mass = mass number, so mass of one particular element
Cations
Ions that carry a net positive charge (due to losing an electron)
Electron deficient, proton rich
Anions
Ions that carry a net negative charge (due to gaining electrons)
Electron rich
Fe^2+
Ferrous Ion
Iron (II)
Fe^3+
Ferric ion
Iron (III)
H-
Hydride
O^2-
Oxide
ClO-
Hypochlorite
NO2-
Nitrite
NO3-
Nitrate
ClO4-
Perchlorate
ClO2-
Chlorite
ClO3-
Chlorate
CO3^2-
Carbonate
PO4^3-
Phosphate
HCO3-
Hydrogen carbonate
H2PO4-
Dihydrogen phosphate
How does electron pull determine energy/stability?
Electrons that are pulled closer to the nucleus have greater attractive force and are more stable
Greater stability means lower energy level of that electron
Less stability means further away from nucleus and higher energy level
How do atoms release energy?
Electrons can move from lower energy states to higher if they absorb energy.
In reverse, this can mean they move from high to low and emit energy (emit a photon)
Emitted energy will be in the form of electromagnetic radiation - this could include visible light, gamma rays, etc.
How do we determine the energy of the electromagnetic radiation?
E = hf H = Planks constant, equal to 6.63 x 10^-34 J.s f = frequency of light
How do we determine frequency of light (f)?
Take the speed of light and divide by it’s wavelength
Speed of light is 3.00 x 10^8 m/s (in a vacuum) or c
f = c/lambda
How do we calculate the amount of energy an electron holds at a certain energy level?
E = - R/n^2 R = 2.18 x 10*-18 J
How do we calculate the energy emitted or absorbed when an electron moves to a new energy level?
hc/lambda = R(1/n(final)^2 - 1/n(initial)^2) = change of energy
What is the principal quantum number?
Corresponds to the energy level of the electron
The principal quantum number corresponds to the row (period) of the table that the element is found
What is the azimuthal number?
Describes the angular momentum and shape of orbit of an electron
Also known as the subshell of the principal quantum number
Can never be greater than n - 1 or less than 0.
denoted as l, but the number than l is equal to determines the subshell
so if l = 0, it’s the s subshell
l = 1, p subshell
l = 2, d subshell
l = 3, f subshell
The types of subshells have different shapes, so
s = sphere
p = dumbbell
d and f = more complex
How do we determine spacial orientation of orbital within subshell?
Magnetic quantum number - gives you the number of orbitals for a given subshell Each orbital can hold up to 2 electrons s = 0 p = -1, 0, 1 d = -2, -1, 0, 1, 2 f = -3, -2, -1, 0, 1, 2, 3
Spin quantum number
Relates to angular momentum - how is the electron moving/oriented within the orbital?
can be -1/2 or 1/2
Two electrons in the same orbital would have the same subshell (so azimuthal number) and magnetic quantum number, but opposite spin quantum numbers
What are exceptions to the Aufbau principal?
Cr and Cu
These don’t have full s orbitals, instead the electrons reside in the p oribals to for [Ar]4s13d5 and [Ar]4s13d10 respectively
What are traits of group 1 on the periodic table?
Alkali metals
include Li, Na, K
Highly reactive - will easily donate their valence electron to form +1 cations
Traits of group 2 elements
alkaline earth metals
Mg, Ca
will donate 2 valance to form 2+ cations
in solid state are reactive
Traits of group 3-12
transition metals
hard, durable metals, easily conduct electricity, take on vivid colors due to electron transitions btwn d orbitals
What are metalloids
share traits of metals and nonmentals
semiconductors
brittle
Ex: Boron, silicon
Group 13 Traits
Some semimetals and some metals
Boron = semimetal, the rest are metals
Group 14 Traits
Belong to the carbon family
have nonmental and metal properties
can form oxides
have 4 valence electrons
Group 15 Traits
Elements of the nitrogen family
5 valence electrons
properties of nonmetals and metals
Group 16 Traits
Chalcogens
include O and S
mostly non-metal characteristics
6 valence, nearly full so they react w/ other elements to form 2- anions
Group 17 Traits
Halogens
v reactive - want to gain their last electron to have a full valence shell
Non-metals
Group 18
Nobel gases
non-metallic, unreactive due to full valence shell
low boiling points
How does attractive force of nucleus on valence electrons change across periodic table?
Zeff = the effective nuclear charge
Zeff increases from left to right across the table (atomic number increases, more protons)
Thus, atomic radius decreases from left to right (more charge to pull in electrons)
However, atomic radius increases from top to bottom of the table, because principal quantum number increases (more shells between nucleus and valence electrons)
largest radii elements are in the bottom left of the table
What is ionic radius?
The radius of the ion form of an element
Cation forms of atoms have a smaller ionic radius than the atomic radius
Anion forms of atoms have a larger ionic radius than the atomic radius
What is ionization energy?
The amount of energy required to remove an electron (and form an ion)
Ionization energy increases as Zeff increases (b/c greater Zeff means you hold electrons more tightly, so takes more energy to remove)
What is electron affinity?
Amount of energy released when an electron is added to an electron
increases as Zeff increases (exception is noble gases), also decreases top to bottom of the table
What is electronegativity?
Tendency for an atom to attract electrons that are shared in a chemical bond btwn two atoms
High electron affinity means high electronegativity, so this also increases as Zeff increases, but decreases down the table (top to bottom)
2 e rich, 2 bonded atoms, 0 lone
Linear, 180
Ex: co2
3 e rich, 3 bonded atoms, 0 lone
Trigonal planar, 120
Ex: BF3
4 e rich, 4 bonded atoms, 0 lone
Tetrahedral, 109.5, ch4
4 e rich, 3 bond, 1 lone
Trigonal pyramidal, 107, nh3
4 e rich, 2 bond, 2 lone
Bent, 104.5, h2o
5 e rich, 5 bond, 0 lone
Trigonal bipyramidal, 90, 120, 180
6 e rich, 6 bonds, 0 lone
Octahedral, 90, 180
