Answer:
Oxygen is the most contain in earth but you asked in a,b,c and d. So I'll choice A. aluminium.
C) It contains the same number of electrons and protons.
Answer:
B- Iodine
Explanation:
Using the periodic trends, electronegativity (electron affinity) goes down as you go down a period. This is due to the atom gaining new shells when going down each period, resulting in a weakened attraction force between the nucleus and the electrons in the cloud. In other words. as more shells are added, the weaker the atom's affinity for electrons are and the less electronegative it is. As a result, Iodine would have the weakest attraction for electrons in a bond with Calcium as it is the furthest down in the periodic table.
Answer:
The correct answer is option c.
Explanation:
Alkanes with higher molecular mass has higher boiling point.
Thisis because when the molar mass of the alkanes increases the the surface area increases with which van der Waals forces between the molecules of alkane also increase which increases the association of the molecules of with each other which results in increase in boiling point is observed.
The increasing order of the molar mass of the given alkanes;

So out of ethane, pentane and heptane . Heptane has highest molecular mass with higher boiling point value. Where as ethane have the lowest value of boiling point.