Identify the rule (aufbau principle, Hund's rule, Pauli-Exclusion principle) violated by the following electron configurations.

i) Li     1s² 2p¹

ii) O    [He] 2s² 2p ↿↿  ↿   ↿ 

iii) P    [Ne] 3s² 3p ↿⇂  ↿     

Identify which has an incorrect ground-state electron configuration.

Determine the identity of an element that has completely filled the first, second, and third shells and has three electrons in the fourth shell. Is it a metal or a nonmetal? In which orbital is the last electron found?

The electron configurations given below represent excited states. Identify the elements, give their chemical symbols and write their ground state electron configuration.

A. 1s²2s²2p³3s¹

B. [Ar]4s²3d¹⁰4p²5p¹

C. [Kr]5s²4d²5p¹

Which of the following statements are true?

1. Selenium (Se) has the electron configuration [Ar]4s²4d¹⁰4p³.

2. Silver (Ag) has the electron configuration [Kr]5s¹4d¹⁰.

3. Chromium (Cr) has the electron configuration [Ar]4s¹3d⁵.

Provide condensed electron configurations for Se and the most stable ion it forms.

Choose the correct statement on the formation of a strontium ion and the complete octet.

Give the number of valence electrons and group number for livermorium.

Determine the number of inner and valence electrons in an atom of the given elements.

a. O

b. C

c. Fe

d. Mg

e. S

The Lewis dot symbols for M and N are given below. 

Determine the ions formed by M and N.

Consider the following electron configuration by shell of an unknown element: 2 8 18 18 7. 

(i) This element belongs to which group and period in the periodic table?

(ii) Determine whether the element is a metal or a nonmetal.

(iii) Determine the number of protons in an atom of this element.

(iv) Provide the identity of the element.

(v) Draw the electron-dot symbol of this element.

Based on the condensed electron configurations and Lewis electron-dot symbols, predict the ions formed from the following atoms and determine the formula of their compound.

Ba and O

Consider the elements of Group 5A (the "nitrogen family"): N, P, As, Sb, Bi, and Mc. What is the trend in metallic character going down this group? What is the trend in metallic character going from left to right across a period?

Identify and explain the trend observed for the atomic radius when moving from top to bottom in the same column on the periodic table.