Atomic Structure

Question 1

Atomic Number

Answer 1

• Number of protons in the atom
• Same for atoms of the same element
• Bottom Number in _z^aX

Question 2

Mass Number

Answer 2

• Number of neutrons and protons in an atom
• Top number in _z^aX

Question 3

Nucleus

Answer 3

• Positive charge
• Made of protons and neutrons
• Electrons orbit around

Question 4

Isotopes

Answer 4

• Same element, same # of P, different # of N
• Different mass number
• Usually same chemical properties

Question 5

Ernest Rutherford

Answer 5

• 1911 gold foil experiment found dense, positively charged nucleus

Question 6

Valence Electrons

Answer 6

• Outer ring of e-
• Determine atom reactivity
• Farther from nucleus = more reactive

Question 7

Cation

Answer 7

• Positively charged ion, has lost e-

Question 8

Anion

Answer 8

• Negatively charged ion, has gained e-

Question 9

Protons

Answer 9

• +1 charge
• Mass 1 amu
• Symbol 1/1(H)
• Located in the nucleus

Question 10

Neutrons

Answer 10

• No charge
• Mass 1 amu, slightly larger than P
• Symbol 1/0(N)
• Located in nucleus, forms isotopes

Question 11

Electrons

Answer 11

• -1 charge, neutral atom #e- = #P
• Symbol e-
• Mass is 1/1837 of P, negligible
• Located in orbitals, outer is valence

Question 12

Atomic Mass Units

Answer 12

• 1/12th the mass of a C-12 atom, so N and P are both 1 amu 1.66x10^-24 g

Question 13

1 Mole

Answer 13

• The number of atoms in 12g of C-12
• 6.022 x 10^23 atoms = 1 mol
• Avogadro’s number

Question 14

Atomic Mass

Answer 14

• Mass in grams of 1 mole of atoms
• 1 amu = 1 g / 6.022 x 10^23
• Number below symbol on periodic table, weighted average of isotope masses

Question 15

Weighted Average

Answer 15

(Percent as decimal)(amu of isotope) + (Percent as decimal)(amu of isotope) …

Question 16

Bohr’s Atomic Model

Answer 16

• e- in orbitals
• Only certain energy levels (and orbits) allowed
• Does not take e- repulsion into account

Question 17

Excited state

Answer 17

• Atom absorbs energy and e- moves to a higher energy level

Question 18

Ground state

Answer 18

• Atom releases energy and e- moves to lower energy level

Question 19

Quantum Mechanic Atom Model

Answer 19

• e- in a state of rapid motion within regions of space around nucleus called orbitals

Question 20

Heisenberg Uncertainty Principle

Answer 20

• Impossible to determine momentum and position of e- simultaneously with accuracy

Question 21

Principal Quantum #

Answer 21

• Principle quantum number= n
• Orbital size and distance from nucleus
• Larger number = higher energy
• Max e- in shell is 2n^2

Question 22

Azimuthal/ Angular Momentum Quantum #

Answer 22

• Azimuthal (angular momentum) quantum number= L: subshells and shape
• L= 0 → (n-1) 0=s 1=p 2=d 3=f
• Greater L = greater energy relative to atom

Question 23

Magnetic Quantum #

Answer 23

• Magnetic Q. #= m_l, orbitals within subshells
• m_l= -L→L including 0

Question 24

Spin Quantum #

Answer 24

• m_s= -1/2 or +1/2
• e- is spinning downwards or upwards
• 2e- per orbital (m_l)

Question 25

Pauli Exclusion Principle

Answer 25

• Whenever two e- are in the same orbital they must have opposite spins
• Same spin different orbital = parallel spins
• Same orbital different spin = paired

Question 26

Electron Configuration

Answer 26

2p⁴

• n = 2
• sublevel l = p
• # of e- in sublevel = 4

Question 27

Orbital Filling

Answer 27

• Lowest to highest energy level
• (n + L) gives the energy level
• To determine what sublevels are filled know the atom’s # of e-

Question 28

Hund’s Rule

Answer 28

• Within a given subshell, orbitals must be all filled with one e- with parallel spins before they are paired with another
• e- avoid pairing since - - repels

Question 29

Paramagnetic

Answer 29

• Materials with unpaired e- form a weakly attractive magnetic field

Question 30

Diamagnetic

Answer 30

• Materials with no unpaired e- are slightly repelled by a magnetic field