Question

1. which of the elements is least likely to form a positive ion?
2. as you move down a group on the periodic table, what happens to the atomic radius?
3. which property generally decreases as you move from left to right across a period?
4. which element would have the highest electronegativity?
5. which group contains elements that are mostly gases at room temperature?
6. what is the correct order of increasing atomic size among the following elements: li, na, k?
7. which element is expected to have the lowest ionization energy in period 5?
8. who organized their periodic table according to atomic number in 1913?
9. which of the following elements would be considered a metalloid?
10. which element has the lowest electronegativity in group 2?
11. when dr. mendeleev created the first periodic table, what did he base it on?

Explanation:

1. Noble - gas elements have a full - valence shell and are least likely to form positive ions.
2. As you move down a group on the periodic table, the number of electron shells increases, causing the atomic radius to increase.
3. Atomic radius generally decreases as you move from left to right across a period due to increased nuclear charge pulling electrons closer.
4. Fluorine has the highest electronegativity among elements due to its small size and high nuclear charge.
5. Group 18 (noble gases) contains elements that are mostly gases at room temperature.
6. In the same group, atomic size increases down the group. So the order is Li < Na < K.
7. In a period, the element on the leftmost side has the lowest ionization energy. In Period 5, it is rubidium (Rb).
8. Henry Moseley organized the periodic table according to atomic number in 1913.
9. Examples of metalloids include boron (B), silicon (Si), germanium (Ge), etc.
10. In Group 2, barium (Ba) has the lowest electronegativity as electronegativity decreases down a group.
11. Mendeleev created the first periodic table based on atomic mass and recurring chemical properties.

Answer:

1. Noble - gas elements
2. The atomic radius increases.
3. Atomic radius
4. Fluorine
5. Group 18
6. Li < Na < K
7. Rubidium (Rb)
8. Henry Moseley
9. Boron (B), silicon (Si), germanium (Ge) etc.
10. Barium (Ba)
11. Atomic mass and recurring chemical properties