Unit 2: Atoms Flashcards
nucleus
Contains all of the positive charge and most of the mass of a atom
Central core of an atom which contains the protons (1 or more) and neutrons
atomic number
The number of protons in the nucleus of an atom of a given element
orbital (Schrödinger Model)
3-dimensional region of space with a good chance of containing an electron
Schrödinger’s model is very mathematical; electrons are described in terms of wavefunctions and probabilities rather than absolute positions
Electrons do not live in orbits, they live in orbitals
abbreviated electron configuration
AKA core notation
Core electrons are substituted by the symol of the noble gas in square brackets
EX: Mg = [Ne] 3s2
What is a group in the periodic table?
A column in the periodic table
AKA family
Elements in the same column of the periodic table have similar chemistry
Many families have special names; elements in a family often have similar names due to their similar reactivity
What is a period in the periodic table?
A row in the periodic table
Elements in the same row of the periodic table have different chemistry
core electrons
All of the electrons that are not in the highest energy level, these electrons are very stable and will rarely get involved in reactions
photon
A “unit” or “packet” of radient energy
A particle representing a quantum of light or other electromagnetic radiation
A photon carries energy proportional to the radiation frequency but has zero rest mass
Have wavelength properties, they travel through space as oscillating electric and magnetic fields
Planck’s constant
Special value in quantum mechanics
Symbol: h
Value: 6.626 x 10-34 Js
orbital energy diagram
A conventient tool for understanding the energy of orbitals
The boxes are arranged from bottom to top in order of increasing energy
chemical reaction
Chemical change
A process in which 1 or more substances are converted into new substances that have compositions and properties different from those of the original substance
Cannot change the number of protons or neutrons in any atoms but easily changes the number of electrons
classical mechanics
Developed by Isaac Newton
A mathematical model for the rules governing the motion of bodies
continuous spectrum
A spectrum in which all the visible wavelengths are present
Violet: 400nm
Red: 750nm
eletromagnetic radiation
AKA radiant energy, light
Form of energy carried by photons, a “unit” or “packet” of radiant energy
A form of energy that can be described in terms of oscillating waves that move through space at the speed of light
electron
A negatively charged particle “inside” of the atom
All electrons are identical and all atoms “contain” electrons
electronic transitions
Occurs when an electron “moves” from one orbit to another (Bohr model)
When an electron absorbs energy it moves to a higher orbit (n increases)
When an electron emits energy it moves to a lower orbit (n decreases)
proton
Has a positive charge
Number of protons is identity of an element
Charge: +1.6022 x 10-19C
Relative charge: +1
Mass: 1.6726219 x 10-24g (1,836 times more than an electron)
quantized
Can have only certain values
Bohr suggested that the energies of electrons in an atom are quantized.
quantum mechanics
Highly mathematical topic that describes the behavior of electrons in an atom (we’ll ignore the math and work with descriptive terms and memorization)
Quantum numbers = address of electrons
speed of light
All photons travel at the same velocity - the speed of light
Symbol: c
Value: 3.0 x 108 m/s
white light
A source that contains all wavelengths of light
nuclear reaction
Can alter the total amount of mass but this is only important in very high energy environments like a star
ion
Charged atom
Contains a different number of protons and electrons
The charge of an ion is equal to the difference
isotope
Atoms that share the same number of protons but a different number of neutrons are known as isotopes of the same element
Isotopes disprove one of Dalton’s postulates - that all atoms of an element have the same mass
isotope symbol
Communicates the full subatomic structure of an isotope by listing the mass number, atomic number and element symbol
line spectra of the elements
Bohr model of the atom
The line spectra of the elements were collected by placing a small sample of an element in an evacuated glass tube, passing an electric current through the tube to produce excited atoms, collecting the light emitted from the tubes as the atoms relax to the ground state, and passing that light through a prism.
The data collected shows that excited atoms produces a line specrum rather than a continuous spectrum
Atoms cannot emit any arbitrary amount of energy, only certain special amounts of energy can be involved.
mass number
Total number off protons and neutrons in the nucleus
neutral atom
Contais the same number of protons and electrons
neutron
Similar to proton but carries no charge
Found in 1932 by James Chadwick
Number of neutrons is not specific to an element; determines the isotope
Charge: 0C
Relative charge: 0
Mass: 1.6749 x 10-24g (tiny bit more than proton)
atomic mass
Mass (in grams) of 1 mole of that element
Population weighted average of the isotopic masses for that element
Dalton’s Atomic Theory
4 postulates:
- All matter is composed of exceedingly small, indivisible particles called atoms
- All atoms of a given element are identical both in mass and in chemical properties
- Atoms are not created or destroyed in chemical reactions
- Atoms combine in simple, fixed, whole-number ratios to form compounds
* underlined items were proven wrong *
valence electrons
Electrons that are not core electrons
Reside in the highest energy level and are the least stable electrons in the atom
All of the chemistry that an element does depends on the number of valence electrons it contains
The number of valence electrons equals the roman numeral in the column name. EX: P is in VA(15) so it has 5 valence electrons
energy of light
The energy carried y a photon is directly proportional to its frequency
Symbol: E
Units: J (joules)
angular momentum quantum number
Second quantum number, Schrödinger Model
Determines the shape and energy sublevel of an orbital
Symbol: l (lower case l)
Values: 0, 1, 2, … n-1
For values of n, there are 1 or more values of l
metallic character
Periodic trend - metallic character increases:
- from right to left
- from top to bottom
Hund’s rule
States that electrons are distributed into orbitals of equal energy in a way that maximizes unpaired electrons
EX: p orbital for Nitrogen
Oil Drop Experiment
Conducted by Robert Millikan in 1909 to measure the mass and charge of the electron
Charge of electron: -1.6022 x 10-19 C
Relative charge: -1
Mass: 9.1094 x 10-28 g
aufbau principle
From the German ‘auf bauen’, ‘to build up’
Electrons fill orbitals starting with the lowest-energy orbitals
electron configuration
Notation used to list all the filled orbitals
- orbitals are listed from left to right in order of increasing energy
- given a superscript to the right to indicate how many electrons they contain
- unfilled orbitals are not listed
ionization energy
Measures how hard it is to lose an electron for the different elements (energy needed to make an ion) - valence electrons are much easier to remove than core electrons
Atoms can lose multiple electrons and have multiple ionization energies
Periodic trend - first ionization energy of the elements tend to increase:
- from left to right
- from bottom to top
Plum Pudding Model
Proposed by J.J. Thomson in 1904 to address the negative and positive charge
The model proposed atoms contained electrons embedded in a uniform sphere of positive charge
* Further experiments verified that the atom does contain positive charge BUT it is not a uniform distribution *
Pauli exclusion principle
States that no 2 electrons in an atom can share quantum numbers (address)
A maximum of 2 electrons can occupy each orbital and they must have opposit spins
Bohr Model
Niels Bohr suggested the planetary model of the atom in 1913 to explain the line spectra of the elements; focused on Hydrogen - 1 proton and 1 electron; didn’t work for atoms with >1 electron
Proposed electrons orbit the nucleus of the atom much like planets in the solar system orbit the sun
These orbits were fixed at certain distances and an electron in an orbit was stable
Each orbit was given a value n, a positive integer with 1 being the one closest to the nucleus
The lines in the spectra were the result of electronic transitions
Cathode Ray Experiment
Conducted in 1897 by JJ Thomson
Demonstrated that the atom was not indestructible
Credited with the discovery of the electron
periodic table and electron configurations
Each row of the periodic table represents a value of n - d orbital is off by 1 and f by 2
Each block of the periodic table represens a value of l
The number of columns in each block is determined by the values of m and ms
spin magnetic quantum number
Fourth quantum number
Determines the spin of the electron
Symbol: ms
Values: +/- 1/2 (has only 2 values
Each orbital can contain 2 electrons of opposite spin, this is usually drawn as arrows pointing up and down within a box on an orbital diagram
diatomic elements
Found in nature as 2 atoms bound together, rather than as single atoms
Have H2 Hydrogen
No N2 Nitrogen
Fear F2 Flourine
Of O2 Oxygen
Ice I2 Iodine
Cold Cl2 Chlorine
Beer Br2 Bromine
electromagnetic spectrum
All the different forms of electromagnetic radiation
principal quantum number
First quantum number, Schrödinger Model
Determines the size and energy level of an orbital
Symbol: n
Value: any positive integer (1, 2, 3, …)
Gold Foil Experiment
Demonstrated that the atom is not uniformly positive
Conducted in 1908 by Ernest Rutherford
The positive charge of the atom is contained in a very small region at the center of the atom
law of conservation of mass
Matter cannot be created or destroyed during a chemical reaction (except in nuclear reactions)
It can change forms during a reaction but there will always be the same total amount
1787 - experimental work by Antoine Lavoisier led to the law
law of conservation of energy
During a chemical or physical change, energy can be transferred or it can change forms but the total amount of energy remains constant, it cannot be created or destroyed
law of definite proportions
All samples of a given compound contain the same proportion, by mass, of the elements they contain
EX: Water (H2O) contains the same proportion of hydrogen and oxygen no matter where the sample comes from
Mass Ratio: 8:1
Volume Ratio: 1:2
1804 - experiemental work of Joseph Proust led to the law
law of multiple proportions
In circumstances where 2 or more elements make a series of compounds together, the relative mass proportions of the elements follows a pattern
EX: water (H2O) and hydrogen peroxide (H2O2) both contain H & O
If a water sample has 2 g of H, it has 16g of O
If a hydrogen peroxide sample has 2 g of H, it has 32g of O
The ratio of masses of O between the two is 1:2 which is a small-whole number ratio
1808 - experimental work of John Dalton led to the law
magnetic quantum number
Third quantum number, Schrödinger Model
Determines the orientation of an orbital and the total nuber of orbitals in an energy sublevel
Symbol: m
Values: -l, -l+1, … , 0, …, l-1, l
For each value of l, there are 1 or more values of m
frequency
Number of wave cycles that pass a point per second
Symbol: v (Greek letter nu)
Units: Hz (hertz) or s-1 or 1/s (inverse seconds)
The frequency of electromagnetic radiation is inversely proportional to its wavelength
wavelength
Distance between repeating parts of the wave
Symbol: (Greek letter lambda)
Units: m (meters)
The wavelength of electromagnetic radiation is inversely proportional to its frequency
Shrödinger Model
nlm
n = principal quantum number: 1, 2, 3, …
l = angular momentum quantum number: s, p, d, f
m = magnetic quantum number: x, y, z
What are the family names in the periodic table?
prefix units
Prefix__Symbol__Factor giga G 109 mega M 106 kilo k 103 deci d 10-1 centi c 10-2 milli m 10-3 micro µ 10-6 nano n 10-9 pico p 10-12
closed-shell or noble gas electron configuration
The elements tend to gain or lose electrons to achieve a closed-shell or noble gas electron configuration
The charges on the most stable ions of the elements also follows a periodic trend
- elements to the left of the periodic table tend to form stable cations by losing electrons
- elements to the right of the periodic table tend to form stable anions by gaining electrons
cation
An atom that loses an electron and becomes a positively charged ion
Atoms can gain or lose more than one electron but rarely more than 3
EX: Na+
Mg2+
Tend to be smaller than the neutral atoms they came from
What is periodicity of the elements’ physical and chemical properties?
Periodicity was recognized by Dmitri Mendeleev and he used that to create periodic table btw 1869 & 1871
Recurring at intervals
atomic size
The size of an atom is a bit difficult to define because the position of the electrons is not well defined
AKA atomic radius
Atoms get much larger at the beginning of each row and then shrink within the row
anion
An atom that gains an electron and becomes a negatively charged ion
Atoms can gain or lose more than 1 electrons but rarely more than 3
Tends to be bigger than the neutral atoms they came from
atomic mass unit (amu)
1 amu = 1.6606 x 10-24 g
measurement unit for atomic mass
basic unit of mass of atoms and molecules
exacltly 1/12 the mass of 12C atom
