Answer to Question #70920 in General Chemistry for Sharita

Question

You are told that an atom of an element has 10 neutrons and has an atomic mass of 21 (it's a fictional atom) idebfie the block in the periodic table and explain the answe.?

Answer 1

Fundamental properties of atoms including atomic number and atomic mass. The atomic number Z is the number of protons in an atom. The atomic mass depends on the number of nuclear particles: neutrons (particles with zero charge) and protons (particles with positive charge). Atoms have no overall electrical charge. That means that there must be a balance between the positively charged protons and the negatively charged electrons. Atoms must have equal numbers of protons and electrons. So Z=number of protons= number of electrons.
For any element:
Number of Protons = Atomic Number
Number of Electrons = Number of Protons = Atomic Number
Number of Neutrons = Mass Number - Atomic Number
So if atomic mass is 21, and there are 10 neutrons, our fictional atom must be has an 11 protons and 11 electrons.
Periodic table is divided into four blocks, and elements are placed into these blocks based on the sub-shell in which their last electron enters. This classification divides the elements into four types s-, p-, d- and f- block elements.
- s orbitals hold 2 electrons
- p orbitals hold 6 electrons
- d orbitals hold 10 electrons
So electron configuration of fictional atom (corresponds with number of electrons=11) is 1s22s22p63s1[1,2]. The fictional element is in the third period of Periodic Table and refers to the s-element (S-block of Periodic Table).

Answer: s-block

Source:
1. https://oeis.org/wiki/Periodic_table
2. https://en.wikipedia.org/wiki/Electron_configuration