Question

1. which scientist created the 1st periodic table?
2. which scientist said the electrons orbit the nucleus in \shells\?
3. which scientist shot particles at gold foil and stated that \atoms are mostly empty space\?
4. what do you notice about the number of valence electrons as you move from left to right across a row or period in the periodic table?
5. what do you notice about the number of energy levels present as you move down a group or column in the periodic table?
6. sally needs a replacement for lithium for a science experiment. she tries silicon, but it does not work. using what you know about patterns in the periodic table, which advice would you give jallah? a. try a lanthanide series element. b. try a non - metal from the halogen group. c. try an element in the same group as lithium. d. try an element that is a gas.

Explanation:

1. Dmitri Mendeleev is credited with creating the first widely - recognized periodic table.
2. Niels Bohr proposed that electrons orbit the nucleus in "shells".
3. Ernest Rutherford conducted the gold - foil experiment and concluded atoms are mostly empty space.
4. As you move from left to right across a period in the periodic table, the number of valence electrons increases by 1 (from 1 to 8 for main - group elements).
5. As you move down a group in the periodic table, the number of energy levels increases by 1.
6. Elements in the same group have similar chemical properties. Lithium is an alkali metal, so an element in the same group as lithium would be a good replacement.

Answer:

1. Dmitri Mendeleev
2. Niels Bohr
3. Ernest Rutherford
4. The number of valence electrons increases by 1 (from 1 to 8 for main - group elements).
5. The number of energy levels increases by 1.
6. C. Try an element in the same group as lithium.