An element with atomic number 19 will most likely combine chemically with the elements whose atomic number is :

1. 17
2. 11
3. 28
4. 20

Parts (i) to (iv) refer to changes in the properties of elements on moving from left to right across a period of the Periodic Table. For each property, choose the correct answer.

(i) The non-metallic character of the elements :

1. decreases,
2. increases,
3. remains the same,
4. depends on the period

(ii) The electronegativity :

1. depends on the number of valence electrons,
2. remains the same,
3. decreases,
4. increases

(iii) The ionization potential :

1. goes up and down
2. decreases
3. increases
4. remains the same

(iv) The atomic size :

1. decreases,
2. increases,
3. remains the same,
4. sometimes increases and sometimes decreases

Electron affinity is the :

1. Power of an atom to attract an electron to itself.
2. Energy released when an electron is added to an isolated atom in the gaseous state.
3. Energy absorbed when an electron is added to an isolated atom in the gaseous state.
4. Energy required to remove an electron from an isolated gaseous atom.

Which of these statements gives the correct picture regarding halogens and alkali metals with respect to an increase in the atomic number ?

1. Reactivity decreases in alkali metals but increases in halogens.
2. Reactivity increases in both.
3. Reactivity decreases in both.
4. Reactivity increases in alkali metals but decreases in halogens.