Will make brainliest if answer correctly.

why would you expect strontium to be chemically more similar to calcium?
they are in the same family/group.
they are in the same period.
they have the same atomic number.
they have the same atomic mass.

They are in same group/family.

Explanation:

Alkaline earth metals are present in group 2 of periodic table. There are six elements in second group. Beryllium, magnesium, calcium, strontium, barium and radium.

All have two valance electrons but in different energy levels. Thus they have similar chemical properties.

Electronic configuration of calcium.

Ca = [Ar] 4s²

Electronic configuration of strontium.

Sr = [Kr] 5s²

They are present in group two and have same number of valance electrons (two valance electrons) and show oxidation state +2 by loosing two valance electrons. They also show similar reactivity.

They react with oxygen and form oxide.

2Sr  +   O₂   →    2SrO

2Ca +   O₂   →    2CaO

this oxide form hydroxide when react with water,

SrO  + H₂O   →  Sr(OH)₂

CaO  + H₂O   →  Ca(OH)₂

With sulfur,

Sr + S   →  SrS

Ca + S   →  CaS

the correct answer is option d

explanation:

i was wrong its d because they dont use cm when calculating square roots

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.