Unit 1 - Atomic Structure & Properties Flashcards
What is formula mass?
The mass of one of basic unit in a network solid
Expressed in amu
What is molecular mass
The mass of molecules that can exist independently
How do you determine the molar mass for a molecule?
Add up the corresponding masses on the periodic table.
What is the Avogadro’s number?
Number that indicates the number of molecules or atoms in one mole of a substance (6.022 * 10 ^23 mole^-1)
What is a mole?
The fundamental unit for counting particles on the macroscopic level
How do you determine the number of moles with a given mass?
Multiply that amount of mass by the reciprocal of the molar mass.
What is the nucleus made up of?
Neutrons (no charge) and protons (positive charge)
What are the electron shell?
The layers of electrons orbiting the nucleus composed of largely empty space
What is the mass number?
Equals to the number of protons and neutrons of an element (e.g. C has a mass number of 12)
What is the atomic number?
Equals to the number of protons in a neutral atom (e.g. C has an atomic number of 6)
What is an isotope?
Forms of an element that has the same number of protons with differing number of neutrons which exhibits identical chemical properties
What is average atomic mass?
Average of the masses of all the isotopes of an element based on their proportion
What is mass spectroscopy used for?
To compare the masses of isotopes through a process of ionization and acceleration through a magnetic field; lighter isotopes will have a greater degree of deflection
What is a pure sample?
A sample with only particles of one type of atom, molecule, or formula unit
What is a mixture?
A substance that contains particles of more than one type of atoms, formula unit, or molecules not chemically combined
What is the Law of Definite Proportion?
Different pure samples of the same compound will always contain the same proportions of each element by mass
What is mass percent?
Percent by mass of an element in a pure sample of a compound in a substance
How to calculate mass percent?
Mass percent of A = (# of atoms) (A’s atomic mass) / formula weight of a compound * 100
Mass percent of component = (mass of component) / total mass of substance * 100
What is molecular formula?
Chemical formula that provide actual number of each type of atom in a molecule
What is empirical formula?
Chemical formula that provides the relative number of each type of atom in molecule (ratio in the simplest form)
How do you determine the multiplier for the empirical formula?
molar mass divided by the empirical formulas molar mass
What is the usage of combustion analysis?
To analyze the composition of hydrocarbons; carbon composition can be determined by mass of CO2 produced, hydrogen can be determined by the mass of H2O produced, and oxygen can be determined by the difference after C and H have been determined
What are orbits?
Space where electrons move around; only certain orbits exist w/fixed distance away from nucleus
What is the Couloub’s Law?
F= k * q1q2/d^2 q= magnitude of charge associated with a particle d= distance between charged particles
What is the shielding effects?
Electrons located further away from the nucleus are partially shielded by inner core electrons due to electrostatic repulsion.
What is the first ionization energy?
Minimum amount of energy required to remove an outermost, least tightly held electrons from an atom in the gas phase
What is an orbital?
Wave function that describes an electron’s possible positions in 3-D space
What are the 4 possible orbital types and electrons held in each
S- 2
P- 6
D- 10
F- 14
What are isoelectronic species?
Species that share the same electronic configuration but have different radii
What are d-block cations?
Elements in the d-block that lose elements from highest s-sublevels before losing from d-sublevel
What is the Aufbau Principle?
Each orbital can hold max of two electrons spinning in opposite directions
What is the Hund’s Rule?
When you have more than one orbital in a subshell, a single spin up electron is added to each orbital before you start adding spin down electrons.
What is the relationship between first ionization energy and shielding effect?
As average distance increases between the nucleus and electrons, the lower the first ionization energy due to the shielding effect.
What does PES data correspond with?
PES data corresponds with the theory that each electron shell contain subshells.
What is the effective nuclear charge?
Nuclear charge experienced by an electron
Inner core electrons
contained in the inner shells
Valence electrons
contained in the outer shells
First ionization energy pattern in periodic table
Increases as we move from left to right
Decreases as we move from top to bottom
Ionization data suggests that
electrons are arranged in shells
Electron configuration
Notation to write the number of electrons found in chemical species in accordance with orbitals
As the ratio of protons to electrons increases, the forces of attraction on those electrons
increase
Example of d-block cations
Fe2+ [Ar] 3d^6
n = 1 contains
one subshell – 1s
max of 2 electrons
n = 2 contains
two subshells – 2s and 2p
max of 8 electrons
n = 3 contains
three subshells – 3s, 3p, and 3d
max of 18 electrons
n = 4 contains
four subshells – 4s, 4p, 4d, and 4f
max of 32 electrons
2p electrons experience a
greater shielding effect
from the 1s electrons than
do the 2s electrons.
the more effectively the electrons within a sub-shell are able to penetrate the
shielding electrons, the greater the
ionization energy of those electrons.
Periodicity
Predictable physical and chemical trends that
occur as one moves across a period or down a
group in the periodic table.
Atomic Radius
Increases down a group
New shells added, valence electrons are less stable, shielding, greater distance
Decreases across a period
Addition of protons, valence electrons in same shell
Metals lose electrons to form
cations
Nonmetals gain electrons to form
anions
Ionic radius
Cations are smaller than neutral atoms
Anions are larger than neutral atoms
Ionic Radius of Cations
Across a Period from Left to Right
Radii of cations decrease
protons added -> increases force of attraction, increase effective nuclear charge
Ionic Radius of Anions
Across a Period from Left to Right
When you encounter the first anion, the radius
increases dramatically -> expansion of electron cloud
The radii then continue to decrease
protons added -> increases force of attraction, increase effective nuclear charge
First Ionization Energy exceptions
It requires more energy to pull an electron from a full
d-subshell than it does to pull the only electron in a
p-subshell (when in the same period).
• It requires more energy to pull an electron from a full s-subshell than it does to pull the only electron in a p-subshell (when in the same period).
– That single electron is easier to remove
The second ionization potential for an atom is
always
greater than the first.
Every element has one extremely large increase in
ionization energy. This occurs when
electron configuration drops a
principal quantum number
Electron Affinity
The energy change that occurs when an electron is
added to a gaseous atom to form a negative ion.
a measure of how much an element wants to
accept another electron.
If electron affinity is negative, then it
Releases energy -> exothermic
Wants to accept electron
If electron affinity is positive, then it
Requires energy -> endothermic
Does not want to accept electron
Electron Affinity pattern
Increases as we move from left to right
protons added -> increases force of attraction, increase effective nuclear charge
Increases as we move from bottom to top
Larger distance between nucleus and valence electron = less energy
Electron affinity is always positive for elements in
Group 2A and 8A
Highest energy subshell is full
Added electron would be only electron in higher shell -> requires a lot of energy to overcome repulsion
Electronegativity
An element’s ability to attract electrons in a
chemical bond
Electronegativity pattern
Increases from left to right
Increase from bottom to top
Increases as atomic radius decreases
Octet Rule
Elements tend to gain, lose, or share valence electrons to acquire a full octet
Exception - element in period 1 has a full octet of 2 electrons
Metals and non-metals loses electrons to obtain
a full octet
Ionic compounds are formed when
metal cations form electrostatic bonds with non-metal anions.
Ionic Bonding
1-Metals transfer electrons to non-metals and form bonds due to electrostatic attractions
2-Cations and anions form electrostatic bonds based on opposite charges
Recognizing Ionic Compounds
Contain either a metal and a non-metal or polyatomic ions
First word in compound name is metal/ammonium
Naming Ionic Compounds
The positive ion (cation) is written first and takes the same name as the element.
The negative ion (anion) is written last and takes the first part of its elements name and –ide is added to the end.
Some metals can forms cations with
different charges
Roman numerals indicate the
Charge that is carried by the cation when that metal is able to form cations with different charges
Copper(I) sulfide contains
Cu+ cations
Copper(II) sulfide contains
Cu2+ cations
Cations with alternate forms include
Copper -> Cu+ or Cu2+
Iron -> Fe2+ or Fe3+
Lead -> Pb2+ or Pb4+
Most polyatomic ions do not have an
-ide suffix
Only three polyatomic ions end in -ide
CN- Cyanide
OH- Hydroxide
O2 2- Peroxide
Only polyatomic cation need to know about is
Ammonium NH4+
When writing ionic formulas, keep in mind
Ionic compounds are neutral -> all charges sum up to zero
Charges come from associated group in periodic table or list
Parentheses must be used when there is some multiple of a certain polyatomic ion
Charges on ions relate to
group they’re in
Group 1A Group 2A d-block Group 3A Group 4A Group 5A Group 6A Group 7A
\+1 (H can also be –1) \+2 \+1 to +5 (it s’ hard to predict) \+3 (Tl can also be +1) \+4 (Sn and Pb can also be +2) -3 non-metals, +3 and +5 metals -2 non-metals, +2 and +4 metals -1
