Question

1. label the trends in the periodic table that you have seen in this activity: - atomic mass - atomic radius - ionization energy - electronegativity - valence electrons

Explanation:

• Atomic mass: In the periodic table, as we move from left - to - right across a period and from top - to - bottom down a group, the number of protons, neutrons (in most cases) increases. Since atomic mass is approximately the sum of protons and neutrons in an atom, atomic mass increases across a period and down a group.
• Atomic radius: Across a period (left - to - right), the number of protons in the nucleus increases, which increases the electrostatic attraction between the nucleus and the electrons. This causes the electrons to be pulled closer to the nucleus, decreasing the atomic radius. Down a group (top - to - bottom), new electron shells are added. The shielding effect of inner - shell electrons reduces the effective nuclear charge experienced by the outermost electrons, and the atomic radius increases.
• Ionization energy: Across a period (left - to - right), the atomic radius decreases (as explained above), and the effective nuclear charge increases. It becomes more difficult to remove an electron, so ionization energy increases. Down a group (top - to - bottom), the atomic radius increases, and the outermost electrons are more shielded from the nucleus. It is easier to remove an electron, so ionization energy decreases.
• Electronegativity: Across a period (left - to - right), the atomic radius decreases and the effective nuclear charge increases. Atoms have a greater tendency to attract shared electrons in a chemical bond, so electronegativity increases. Down a group (top - to - bottom), the atomic radius increases and the shielding effect increases. Atoms have a lower tendency to attract shared electrons, so electronegativity decreases (with some exceptions like in transition metals).
• Valence electrons: Across a period (left - to - right), for main - group elements, the number of valence electrons increases from 1 (for group 1 elements) to 8 (for noble gases). Down a group (top - to - bottom), the number of valence electrons remains the same for main - group elements (e.g., all group 1 elements have 1 valence electron).

Answer:

• Atomic mass: Increases across a period and down a group.
• Atomic radius: Decreases across a period and increases down a group.
• Ionization energy: Increases across a period and decreases down a group.
• Electronegativity: Increases across a period and decreases down a group (with some exceptions).
• Valence electrons: Increases across a period (for main - group elements) and stays the same down a group (for main - group elements).