Question

pre - lab section

1. define period.
2. define group.
3. define atomic radius.
4. define electronegativity.
5. define ionization energy.
6. how does metallic character change from left to right across a period?
7. how does metallic character change from top to bottom within a group?

Explanation:

1. In the periodic table, a period is a horizontal row. Elements in the same period have the same number of electron - shell levels.
2. A group is a vertical column in the periodic table. Elements in the same group have similar chemical properties due to having the same number of valence electrons.
3. Atomic radius is the distance from the nucleus of an atom to its outermost electron shell.
4. Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.
5. Ionization energy is the energy required to remove an electron from a gaseous atom or ion.
6. Across a period from left to right, metallic character decreases. This is because as the number of protons increases, the effective nuclear charge increases, making it harder for atoms to lose electrons.
7. Within a group from top to bottom, metallic character increases. This is due to the addition of electron shells, which makes it easier for atoms to lose electrons.

Answer:

1. A horizontal row in the periodic table where elements have the same number of electron - shell levels.
2. A vertical column in the periodic table with elements having similar chemical properties due to the same number of valence electrons.
3. The distance from the nucleus of an atom to its outermost electron shell.
4. A measure of the tendency of an atom to attract a bonding pair of electrons.
5. The energy required to remove an electron from a gaseous atom or ion.
6. Metallic character decreases from left to right across a period.
7. Metallic character increases from top to bottom within a group.