A. The number of valence electrons increases as atomic mass increases. == Generally true for the representative elements since atomic mass generally increases with increasing Z.
B. The reactivity of alkali metals increases as atomic mass increases. == True. Atomic mass increases down the column and so does reactivity
C. The reactivity of the halogens increases as atomic mass increases. == False. Reactivity decreases down the column.
D. The number of valence electrons decreases across a period. == False. In general, the number of valence electrons increases across a period, particularly for the representative elements.
They would react to form:
Potassium Chlorate + Calcium Oxide
Here is an attachment with the skeleton equation and balance:
You look at the atomic mass.. The number of neutrons is different for different individual atoms of the same element, each atom is also known an isotope. Looking at a periodic table, the atomic mass listed is the average atomic mass for all isotopes of that element found in nature.
Answer: 4.52x10²⁴ atoms Li
Explanation: For 1 mole of Li it is equal to the Avogadro's Number.
Solution:
7.5 moles Li x 6.022x10²³ atoms Li/ 1 mole Li
= 4.52x10²⁴ atoms Li
