Question

Elements with valency 1 are:
A. always metal
B. always metalloids
C. either metals or non-metals
D. always non-metals

Answer 1

Valency can be 1 in two cases, one is when the number of electrons in the outermost shell are 1 and the other case is when the electrons in the outermost shell are 7.

Complete step by step answer:
-There are 7 periods and 18 groups in periodic tables where atoms are arranged on the increasing order of their atomic number because the atomic number gives us the number of electrons of the atom. Electrons only decide the chemical properties of an atom as they are loosely held by the atom.
-Along the period, the atomic number increases and so does the number of electrons without altering the number of shells of atoms. So the number of electrons keep on adding as we go from left to right across a period.

-Valency is the number of the electrons present in the outermost shell of an atom which is also called the valence shell of an atom. Those electrons are important to be studied as they are the most loosely held electrons of the atoms.
-So, valency is the number of outermost electrons of the atom. It states the combining capacity of the atom. It can be found if we know the atomic number of an atom as it tells us the total number of electrons present in the atom.
Atomic no. = No. of proton = No. of electron

-The number of electrons to be filled in each shell depends on Aufbau’s principle and Hund’s rule. Valency tells us only the total number of electrons present in the outermost shell of the atom and so it is different from the atomic number.
-Along the group, the atomic number increases by 1 and so the last electron always enters the outermost shell of the atom. Thus we can say that the outermost electrons called the valence electrons increase from left to right across a period.
-Valency does not always represent the number of outermost electrons. This is true only when the number of outermost electrons are in the range of 1 to 4. If the outermost electrons are more than 4, then the valency is found by subtracting those electrons from 8.

- If the outermost electrons are 7, then the valency is 8-7=1, not 7
If the outermost electrons are 6, then the valency is 8-6=2, not 6.
So, we see that valency can be the same for group 1 as well as group 17 elements, group 2 as well as group 16 elements and group 3 as well as group 15 elements.
So, the correct answer is “Option C”.

Note: Down the group, the number of shells increase but the valence electrons remain the same. Atomic size increases down the group. This increases the distance between the nucleus of an atom to the valence electrons and leads to changes in many properties like electronegativity, electron affinity, ionization potential.