Which statement about atoms of elements in the same group of the periodic table is true?
they have similar chemical properties and the same number of valence electrons. they have the same number of protons and the same mass.
they have the same number of energy levels and the same amount of reactivity. they have the same number of electrons and the same atomic radius size.

Option (a) is the correct answer.

Explanation:

Chemical properties are defined as the properties which tend to show change in chemical composition of a substance.

For example, toxicity, reactivity, combustion etc are all chemical properties.

Since, elements which belong to same period show similar chemical properties.

This is because elements that lie in the same group have same number of valence electrons. Hence, they tend to show same type of reactivity which makes them exhibit similar chemical properties.

Thus, we can conclude that the statement they have similar chemical properties and the same number of valence electrons, is true about atoms of elements in the same group of the periodic table.

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g

cytokinesis is the splitting of a cell membrane to form 2 identical daughter cells. it's similar to mitosis as both cells have identical copies of dna and cytokinesis is a step in the mitotic cycle.