An atom has 18 protons, 18 electrons, and 20 neutrons. This atom has _____.

A) a negative charge B)an atomic number of 20 C)a mass number of 38 D) a positive charge

Which one of these is the answer?

Q. Any chemical element (X) can be represented as${}_Z{X}^A$ where ‘Z’ is an atomic number and ‘A’ is the mass number. The Atomic number refers to the number of protons and the mass number refers to the sum of protons and neutrons in an atom. For an element, calcium which has 20 protons and 20 neutrons, identify the correct representation:

Q. An atom has 17 electrons, 17 protons, 18 neutrons. Therefore which of the following is/are true?
(a) Its atomic number is 17
(b) Its mass number is 35

Q.

Question 110 (i)

Science Application An atom consists of charged particles called electrons and protons. Each proton has a charge of +1 and each electron has a charge -1. Remember the number of electrons is equal to the number of protons, while answering this question :
What is the charge on an atom?

Q.

Fill in the blanks in the following statements :

(a) The number of protons in the nucleus of an atom is called its ....................

(b) The total number of protons and neutrons in the nucleus of an atom is called its ....................

(c) An atom has atomic mass number 23 and atomic number 11. The atom has .................... electrons.

(d) An atom of an element has 11 protons, 11 electrons and 12 neutrons. The atomic mass of the atom is ....................

(e) If the nucleus of an atom has atomic number 17, mass number 37 and there are 17 electrons outside the nucleus, the number of neutrons in it is ....................

(f) Almost all the mass of an atom is concentrated in a small region of space called the ....................

(g) Cathode rays are a beam of fast moving ....................

(h) The anode rays obtained from hydrogen gas consist of particles called ....................

(i) The maximum number of electrons that can be accommodated in L shell are ....................

(j) The maximum number of electrons that can go into the M shell is ....................

(k) The subatomic particle not present in a hydrogen atom is ....................

(l) The electron has .................... charge, the proton has .................... charge, and the neutron has .................... charge.