Unit 3

Question 1

Atomic theory

Answer 1

1. All matter is composed of atoms.
2. The atoms of a given element differ from the atoms of all other elements.
3. Chemical compounds consist of atoms combined in specific ratios. Only whole atoms can combine.
4. Chemical reactions change only the way atoms are combined in compounds.

Question 2

Subatomic particles

Answer 2

Protons + charge
Neutrons electrically neutral (similar mass to proton)
Electrons - charge
Mass is only 1/1836 of proton

Question 3

Atomic mass unit (amu)

Answer 3

Unit for describing the mass of an atom, based on the mass of a carbon-12 atom
Proton +1 charge
Neutron 0 charge
Electron -1 charge

Question 4

Subatomic particles arranged:

Answer 4

Protons and neutrons packed tightly in nucleus
Electrons surround the nucleus and move rapidly through large volume of space

Question 5

Atomic number
Mass number

Answer 5

Atomic number = #protons
Mass number = p+n
In a neutral atom p = e

Therefore,
N = mass# - atomic#

In textbook mass # A
Atomic # Z

Question 6

Isotopes

Answer 6

Atoms of the same element
Have different mass numbers
Same # of protons but
Different # of neutrons
Can be distinguished by their atomic symbols
Ex. Isotope favor uranium identified as U-235 to uranium-235

Question 7

Metal

Answer 7

A malleable element, with a lustrous appearance, that is a good conductor of heat and electricity
– Metals occur on the left side of the periodic table.

Question 8

Nonmetal

Answer 8

An element that is a poor conductor of heat and electricity
– Nonmetals occur on the upper- right side of the periodic table.

Question 9

Metalloid

Answer 9

An element whose properties are intermediate between those of a metal and a nonmetal
– Metalloids are located in a zigzag band between the metals on the left and nonmetals on the upper- right side of the periodic table.

Question 10

Elements in the same vertical column (group)

Answer 10

Have similar physical and chemical properties

Question 11

Group 1A—Alkali metals

Answer 11

• Shiny, soft metals with low melting points
• React with water to form products that are highly alkaline
• Highly reactive
• never found in nature in a pure state.

Question 12

Group 2A—Alkaline earth metals

Answer 12

• Lustrous, silvery metals
• Less reactive than their neighbors in group 1A
• Never found in nature in a pure state

Question 13

Group 7A—Halogens

Answer 13

• Colorful and corrosive nonmetals
• Found in nature only in combination with other elements, such as with sodium in table salt (sodium chloride, NaCl)

Question 14

Group 8A—Noble Gases

Answer 14

• Colorless gases
• Labeled the “noble” gases because of their lack of chemical reactivity

Question 15

Valence electrons and group number

Answer 15

Elements in the same group have similar chemical properties because they have the same number of valence electrons and can undergo the same types of chemical reactions

Question 16

Periodicity

Answer 16

Repeating rise and fall pattern

Question 17

Metallic character
Trend

Answer 17

atoms that lose electrons easily to form ions have more metallic character and relates to the ionization energy of elements.
Increases from top to bottom and right to left

Question 18

Atomic radius trend

Answer 18

Increases from top to bottom and right to left

Question 19

Ionization energy trend

Answer 19

Increases from bottom to top and from left to right on periodic table
• energy absorbed to remove one electron from a single atom in the gaseous state.

Question 20

Electron affinity trend

Answer 20

Increases from bottom to top and from left to right on periodic table
Energy released on adding an electron to a single atom in the gaseous state

Question 21

Quantum mechanical model developed by Erwin Schrodinger

Answer 21

Helps us understand the electronic structure of atoms:
• Electrons have both particle-like and wavelike properties.
• The behavior of electrons can be described using an equation
called a wave function.
• Electrons are not perfectly free to move. They are restricted to
certain energy values, or quantized.

Question 22

Periodic trends

Answer 22

Question 23

Electrons and energy levels

Answer 23

• Electrons with the same energy are grouped in the same
energy level.
• Electrons farther away from the nucleus— increase in
energy as the value of n increases
• Shells farther from the nucleus can hold more electrons

Wave functions also provide an electron with an “address” within an atom, composed of shell, subshell, and orbital.
Shell/Principal Energy Level (n): A grouping of electrons in an atom according to energy
Shell number (n): 1 2 3 4
Electron capacity: 2 8 18 32

Question 24

Sublevels

Answer 24

-The arrangement of electrons determines the physical and chemical properties of an element.
• Each energy level/shell (n) consists of one or more sublevels.
• The number of sublevels in an energy level is equal to the principal quantum
number (n) of that energy level.
•So, if n =1,then 1 sublevel
• n=2, then 2 sublevels, etc.
• The sublevels are identified as s, p, d, and f.
• The order of sublevels in an energy level is
s<p<d<f
(electrons in s sublevel have least E, those in f have most E)

Question 25

Pauli exclusion principle states that

Answer 25

-each orbital can hold a maximum of two electrons.
-electrons in the same orbital repel each other.
-electrons in the same orbital must have their magnetic spins cancel (they must spin in opposite directions).
-We can represent magnetic spins with arrows

Question 26

Electronic structure of atoms

Answer 26

• s subshell has 1 orbital
• p subshell has 3 orbitals
• d subshell has 5 orbitals
• f subshell has 7 orbitals.

Each orbital holds two (2) electrons, which differ in a property known as spin.

Question 27

Orbital diagrams

Answer 27

• are arranged in the orbitals of an atom.
• fill the orbitals and energy levels from lowest to highest energy level.
• fill orbitals within the same sublevel one at a time, before pairing the electrons.

Question 28

Equation for electrons in each energy level

Answer 28

2n^2
N= energy level

Question 29

Aufbau Principle

Answer 29

Electrons fill orbitals from the lowest-energy upward

Question 30

Pauli’s Exclusion

Answer 30

Each orbital can hold only two electrons, which must be of opposite spin

Question 31

Hund’s Rule

Answer 31

Two or more orbitals with the same energy are each half-filled by one electron before any one orbital is completely filled

Question 32

The number of electrons in each subshell is indicated by

Answer 32

The superscript

Question 33

Lewis Electron-dot symbol

Answer 33

Atomic symbol with dots placed around it to indicate the number of valence electrons

Question 34

Dalton’s atomic theory

Answer 34

1. All matter is made of atoms. Atoms are indivisible and indestructible.
   
   2. All atoms of a given element are identical in mass and properties
   3. Compounds are formed by a combination of two or more different kinds of atoms.
   4. A chemical reaction is a rearrangement of atoms.

Question 35

Modern atomic theory

Answer 35

1. All matter is composed of atoms.
   
   2. The atoms of a given element differ from the atoms of all other elements.
   3. Chemical compounds consist of atoms combined in specific ratios. Only whole atoms can combine.
   4. Chemical reactions change only the way atoms are combined in compounds.

Answer 36

The discovery of the electrons during a cathode experiment, proved that the atom wasn’t indivisible since the atom had even smaller units. Later the gold foil experiment gave us a better idea of how the sub particles are arranged.

Question 37

Isotope symbols

Answer 37

A = mass number
Z = atomic number (# of p)

Question 38

Electron affinity

Answer 38

Amount of energy released upon accepting an electron
Has to do with atoms ability to steal electrons from other atoms

Question 39

The Bohr model of atoms

Answer 39

has individual energy levels from n=1 up to n=7.
The principal energy levels correspond to the periods on the periodic table

Question 40

Quantum theory of electron configuration

Answer 40

principal energy levels are split into sublevels or subshells that group electrons based on the amount of energy they have.
Sublevels/subshells are organized into orbitals that are represented by three-dimensional shapes related to the probability of finding an electron within the sublevel based on the electron’s energy.