Chapter 1: atomic structure

Question 1

What are the three subatomic particles?

Answer 1

• A proton has a positive charge and a mass around 1 amu
• A neutron has no charge and a mass around 1 amu
• An electron has a negative charge and a negligible mass

Question 2

Nucleus

Answer 2

Contains the protons and neutrons, while the electrons move around the nucleus

Question 3

Atomic number

Answer 3

The number of protons in a given element

Question 4

Mass number

Answer 4

The sum of an element’s protons and neutrons

Question 5

Atomic mass

Answer 5

Is essentially equal to the mass number, the sum of the element’s protons and neutrons

Question 6

Isotopes (and name of H isotopes)

Answer 6

Isotopes are atoms of a given element (same atomic number) that have different mass numbers- they differ in the number of neutrons

• Most isotopes are identified by the element followed by the mass number (such as carbon-12, carbon-13, etc)
• The three isotopes of hydrogen have different names: protium, deuterium, and tritium

Question 7

Atomic weight

Answer 7

The weighted average of the naturally occurring isotopes of an element. The periodic table lists atomic weights NOT atomic masses

Question 8

Rutherford’s theory

Answer 8

First postulated that the atom had a dense, positively charged nucleus that made up only a small fraction of the volume of the atom

Question 9

Bohr Model of the atom

Answer 9

A dense, positively charged nucleus is surrounded by electrons revolving around the nucleus in orbits with distinct energy levels

Question 10

Define quantum

Answer 10

The energy difference between energy levels is a quantum.

• Firs described by Planck

Question 11

Quantization

Answer 11

This means that there is not an infinite range of energy levels available to an electron; electrons can exist only at certain energy levels.

• The energy of an electron increases the farther it is from the nucleus

Question 12

Atomic absorption spectrum

Answer 12

The atomic absorption spectrum of an element is unique; for an electron to jump from a lower energy level to a higher one, it must absorb an amount of energy precisely equal to the energy difference between the two levels

Question 13

Atomic emission spectrum

Answer 13

When electrons return from the excited state to the ground state, they emit an amount of energy that is exactly equal to the energy difference between the two levels; every element has a characteristic atomic emission spectrum.

• Sometimes the electromagnetic energy emitted corresponds to a frequency in the visible light range.

Question 14

Quantum mechanical model

Answer 14

Posits that electrons do not travel in defined orbits but rather are localized in orbits

• An orbital is a region of space around the nucleus defined by the probability of finding an electron in that region of space

Question 15

Heisenberg uncertainty principle

Answer 15

States that it is impossible to know both an electron’s position and its momentum exactly at the same time

Question 16

Quantum numbers

Answer 16

There are four quantum numbers, which completely describe any electron in an atom

• The principle quantum number (n) describes the average energy of a shell
• The azimuthal quantum number (l) describes the subshells within a given principal energy level (s, p, d, f)
• The magnetic quantum number (m_l) specifies the particular orbital within a subshell where an electron is likely to be found at a given moment in time
• The spin quantum number (m_s) indicates the spin orientation (+/- 1/2) of an electron in an orbital

Question 17

Electron configuration and spectroscopic notation

Answer 17

The electron configuration uses spectroscopic notation (combining the n and l values as a number and letter, respectively) to designate the location of electrons

Ex: 1s²2s²2p⁶3s² is the electron configuration for magnesium: which has 12 electrons

Question 18

n + l rule

Answer 18

This rule can help determine how electrons fill the principal energy levels and subshells according to increasing energy

Question 19

Hund’s rule

Answer 19

Electrons fill orbitals according to Hund’s rule: states that subshells with multiple orbitals (p, d, and f ) fill electrons so that every orbital in a subshell gets one electron before any of them get a second

Question 20

Paramagnetic vs Diamagnetic

Answer 20

• Paramagnetic materials have unpaired electrons that align with magnetic fields, attracting the material to a magnet
• Diamagnetic materials have all paired electrons, which cannot easily be realigned: they are repelled by magnets

Question 21

Valence electrons

Answer 21

The electrons in the outermost shell available for interaction (bonding) with other atoms

• For representative elements in Groups 1, 2, and 13-18, the valence electrons are in the s and/or p orbitals
• For transition elements, the valence electrons are found in s and either d or f orbitals