gen chem- Atomic + Electronic Structure

Which of the following electron configurations would have the most similar properties to Si?

A. 1s²2s²2p²

B. 1s²2s²2p⁶3s²

C. 1s²2s²2p⁶3s²3p¹

D. 1s²2s²2p⁶3s²3p⁴

A

• this is the electron configuration for carbon which is in the same group as Si so they share similar chemical properties

What is the maximum number of electrons that can be held in the third energy level?

A. 2

B. 8

C. 10

D. 18

E. 32

D

3s= 2

3d= 10

3p= 6

2+10+6= 18

Which of the following wavelengths has the lowest energy?

A. visible light

B. microwaves

C. infrared radiation

D. gamma rays

E. ultraviolet

B

(lowest energy and highest wavelength) radio waves → microwaves → infrared → visible light → ultraviolet → x-rays → gamma rays (highest energy + shortest wavelength)

mnemonic: Roman Men Invented Very Unusual X-ray Guns

The three common isotopes of nitrogen (N¹³, N¹⁴, and N¹⁵) have

A. the same atomic number an an equal number of neutrons

B. the same atomic number and an equal number of protons

C. the same mass number and an equal number of neutrons

D. the same mass number and an equal number of protons

E. the same mass number and an equal number of electrons

B

• isotopes are atoms of the same elements that have the same number of protons but different number of neutrons (so different mass numbers)

Which of the following is the ground state electron configuration of Mo?

A. [Kr] 5s¹4d⁵

B. [Kr] 5s²4d⁴

C. [Kr] 4s²4d⁴

D. [Kr] 4s²3d⁴

E. [Kr] 4s¹3d⁵

A

• Mo is an exception to the typical e- configuration rules

• instead of fully occupying the 5s orbital, it places one electron in 5s and five electrons in 4d to minimize repulsion and increase stability

How many valence electrons does nickel (Ni) have?

A. 8

B. 9

C. 10

D. 11

E. 12

C

• for elements in the d-block like Ni, the valence electrons include both the electrons in the highest energy s orbital and those in the partially filled d orbital

so 4s2,3d8

2+8= 10

Which of the following would be attracted to an external magnetic field?

A. N₂

B. Xe

C. O₂

D. Cl^-

E. Na⁺

C

• paramagnetic atoms have at least one unpaired e- that attracts them to magnetic fields

• Xe, Cl-, and Na+ don’t have any unpaired e-

mnemonic: No Pair, Odd Oxygen

• N2: No unpaired e- → diamagnetic

• O2: Odd e- (unpaired) → paramagnetic