Which of the following atoms has the weakest attraction for electrons in a bond with a calcium (Ca) atom? a. Br atom
b. I atom
c. Cl atom
d. F atom

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.  

atomic number of carbon is 6

electronic configuration of carbon is 1s²2s²2p²

orbital diagram of c is as shown here in the image.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.