If Z=3, what would be the valency of the element?

If the atomic number (Z) of an element is 3, it means the element has 3 protons and 3 electrons in its neutral state. To determine the valency, we need to look at the electronic configuration. For Z=3, the electronic configuration is 1s²2s¹. This means there are 2 electrons in the 1s orbital and 1 electron in the 2s orbital. The outermost shell (valence shell) is the second shell (n=2), which contains 1 electron. The valency of an element is determined by the number of electrons it needs to gain or lose to achieve a stable octet (or duplet for the first shell). In this case, the element needs to lose 1 electron to achieve a stable configuration like Helium (1s²). Therefore, the valency of the element with Z=3 (Lithium) is 1.