A systematic arrangement of all known chemical elements organized by increasing atomic number into rows (periods) and columns (groups), where elements in the same group share similar chemical properties because they have the same number of valence electrons.
A map of all elements organized so similar ones are in the same column.
Showing a random 20 of 50 problems.
Example 1
easy
Which group does an element with the valence configuration matching 1 outer electron belong to?
Example 2
medium
Which group on the periodic table contains the most reactive nonmetals?
Example 3
medium
An element X is in period 4, group 1. Name X and predict the formula of its chloride.Period 4, Group 1 — identify element X and predict the formula of its chloride
Example 4
hard
Element Q is a metalloid in period 4 sitting on the staircase with 4 valence electrons. Identify Q.
Example 5
easy
Are alkaline earth metals in group 1 or group 2?
Example 6
medium
Why are sodium, potassium, and lithium grouped together in column 1?
Example 7
easy
Which side of the periodic table holds the metals?
Example 8
hard
Which has greater electronegativity: oxygen or sulfur? Explain.
Example 9
medium
As you move left to right across period 2, how does the number of valence electrons change?Valence electrons increase by 1 each step across Period 2
Example 10
hard
Predict the formula of the compound formed between magnesium (group 2) and chlorine (group 17).Mg and Cl ion charges determine the MgCl₂ formula
Example 11
medium
Which has a larger atomic radius: sodium or potassium? Justify.
Example 12
hard
Arrange F, Cl, Br by increasing atomic radius.
Example 13
challenge
Two elements, one in group 1 period 3 and one in group 17 period 3, react. Identify both and predict the compound formula.Group 1 Period 3 + Group 17 Period 3 react — identify both and predict the compound
Example 14
challenge
Element A (period 2, group 1) reacts with element B (period 3, group 17). Identify A, B, the compound, and the ion charges involved.
Example 15
easy
On the periodic table, what do the horizontal rows represent?
Example 16
medium
An element has 2 electrons in shell 1 and 5 in shell 2. Give its period and group.
Example 17
easy
Which element has atomic number 1?
Example 18
easy
What does the period number of an element tell you about its atom?
Example 19
medium
Why do all noble gases sit in the same column?
Example 20
easy
How many periods are in the standard periodic table?