During a chemical reaction the i. total number atoms remains unchanged ii. number of atoms of each type of element remains unchanged iii. total number of chemical bonds remains unchanged 1. i and iii 2. i 3. ii 4. i, ii, and iii 5. i and ii 6. iii

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.