Atomic and Molecular Structure

Question 1

Atom

Answer 1

the basic building block of matter, representing the smaller unit of a chemical element

Question 2

Nucleus

Answer 2

formed by the protons and neutrons, it is the core of an atom

Question 3

Orbitals

Answer 3

this is where the electrons are and is located outside of the nucleus

Question 4

Elements

Answer 4

• composed of very small particles called atoms

- identical in size, mass, and chemical properties

Question 5

Compounds

Answer 5

-composed of atoms of more than one element

Question 6

Chemical Reaction

Answer 6

involves only the separation, combination, or rearrangement of atoms

Question 7

Protons

Answer 7

• carry a single positive charge and have a mass approximately one unified atomic mass unit (amu or u)
• amu is equivalent to one dalton

Question 8

Atomic Number (z)

Answer 8

equal to the number of protons found in an atom of that element

Question 9

Neutrons

Answer 9

-carry no charge and have a mass only slightly larger than that of protons

Question 10

Electrons

Answer 10

• carry a charge equal in magnitude but opposite in sign to that of protons
• has a very small mass

Question 11

Valence Electrons

Answer 11

• shell furthest from the nucleus
• the farther the valence electrons are from the nucleus, the weaker the attractive force of the positively charged nucleus and the more likely the valence electrons are to be influenced by other atoms

Question 12

Mass Number (A)

Answer 12

• equal to the total number of nucleons (protons and neutrons)
• mass number (A) = number of protons + number of neutrons

Question 13

Molecular Weight

Answer 13

the weight in grams per molecule per one mole of a given element (g/mol)

Question 14

Mole

Answer 14

is a unit used to count particles and is represented by Avogadro’s number (6.02x10^23)

Question 15

Isotopes

Answer 15

atoms with the same number of protons but different numbers of neutrons
-ex: 14 C 6 has 6 protons and 8 neutrons

Question 16

Standard Atomic Weight

Answer 16

a weighted average of all the isotopes of an element found naturally on Earth

Question 17

Example Problem (isotopes)

Element Q consists of three different isotopes, A, B, nad C. Isotope A has an atomic mass of 40 u and accounts for 60% of naturally occurring Q. The atomic mass of isotope B is 44 u and accounts for 25% of Q. Finally, isotope C has an atomic mass of 41 u and a natural abundance of 15%. What is the atomic weight of element Q?

Answer 17

0.60(40u) + 0.25(44u) + 0.15(41u) = 24 u + 11 u + 6.15 u = 41.15 u

The atomic weight of element Q is 41.15 g/mol

Question 18

Quantum Theory

Answer 18

• energy emitted as electromagnetic radiation from matter comes in discrete bundles called quanta
• Energy value of a quantum is calculated by the equation: E=hf , h= Planck’s constant 6.626 x 10-34 Js, f= frequency

Question 19

The Bohr Model

Answer 19

E= -Ry/n^2 , Ry = 2.18x10^-18

Question 20

Electromagnetic Energy

Answer 20

E= hc/lambda, c= 3.0x10^8 m/s

Question 21

Line spectrum

Answer 21

each line on the emission spectrum corresponds to a specific electronic transition

Question 22

Balmer series

Answer 22

-four wavelengths in the visible region , n>2 to n=2

Question 23

Lyman series

Answer 23

-higher energy transitions into the UV region

n>1 to n=1

Question 24

Orbital

Answer 24

• a representation of the probability of finding an electron within a given region
• a specific region within a subshell that may contain no more than two electrons

Question 25

Heisenberg uncertainty principle

Answer 25

states that it is impossible to simultaneously determine the momentum and the position of an electron

Question 26

Quantum numbers

Answer 26

n (size of the orbital), l (shape of the orbital), me (orientation of the orbital), ms

Question 27

Pauli exclusion principle

Answer 27

no two electrons in a given atom can possess the same set of four quantum numbers

Question 28

Energy state

Answer 28

the position and energy of an electron described by its quantum numbers

Question 29

Principal Quantum number

Answer 29

• the first quantum number
• denoted by the letter n
• the maximum n that can be used to describe the electrons of an element at its ground state corresponds with that element’s period (row) in the periodic table

Question 30

Azimuthal Quantum number

Answer 30

• the second quantum number
• designated by the letter l
• tells us the shape of the orbitals and refers to the subshells or sublevels that occur within each principal energy level
• for any given n, the value of l can be any integer in the range of 0 to n -1
• the maximum number of electrons that can exist within a subshell is given by the equation 4l + 2

Question 31

Magnetic Quantum number

Answer 31

• the third quantum number
• designated me
• describes the orientation of the orbital in space
• specifies the particular orbital within a subshell where an electron is highly likely to be found at a given point in time
• p subshell has 3 possible ml values (-1,0,+1)
• d subshell has 5 possible ml values (-2,-1,0,+1,+2)
• f subshell has 7 possible ml values (-3,-2,-1,0,+1,+2,+3)

Question 32

Spin Quantum number

Answer 32

• the fourth quantum number
• denoted by ms
• the spin of a particle is its intrinsic angular momentum and is a characteristic of a particle
• the two spin orientations are designated +1/2 and -1/2
• whenever two electrons are in the same orbital, they must have opposite spins due to the Pauli exclusion principle
• electrons in different orbitals with the same ms values are said to have parallel spins
• electrons with opposite spins in the same orbital are often referred to as paired

Question 33

Electron configuration

Answer 33

• the first number denotes the principle energy level, the letter designates the subshell, and the subscript gives the number of electrons in that subshell
• ex: 2p4 indicates there are 4 electrons in the second subshell of the second principal energy level

Question 34

Aufbau Principle

Answer 34

subshells are filled from lowest to highest energy, and each subshell will fill completely before electrons begin to enter the enxt one

Question 35

(n+l) rule

Answer 35

states that the lower sum of the first and second quantum numbers, the lower the energy of the subshell

Question 36

Hund’s Rule

Answer 36

states that within a given subshell orbitals are filled such that there are a maximum number of half-filled orbitals with parallel spins