Question

Neutrons are present in all atoms except?
A.$He$
B.$C$
C.$H$
D.$Ne$

Answer 1

To answer this question, you should recall the basic model of an atom and how the subatomic particles are arranged in an atom. The nucleus contains types of subatomic particles, protons and neutrons. The number of neutrons and protons determine the atomic mass of an element.

Complete step by step answer:
- The model suggests that atoms are made of smaller subatomic particles. In the middle of every atom is the nucleus. The protons have a positive electrical charge and the neutrons have no electrical charge. The third type of subatomic particle, electrons, moves around the nucleus. The electrons have a negative electrical charge.
- An atom usually contains an equal number of positively charged protons and negatively charged electrons. This makes the atom itself electrically neutral. The electrons exist at different energy levels, called shells, around the nucleus. The shell can only accommodate a limited number of electrons. All elements have atoms with neutrons except for one.
- A normal hydrogen atom does not have any neutrons in its tiny nucleus. That tiny little atom has only one electron and one proton. Hydrogen's special structure becomes very important when you learn how hydrogen interacts with other elements in the periodic table.

Hence, the correct answer to this question is option C.

Note:
Make sure you remember the difference between isotopes, isotone, isobars and isoelectronic species. Isotopes refer to the atoms of the same element having the same atomic number but different mass numbers. According to Moseley’s law, the chemical properties of an element depend on the number of electrons present and their configuration within an atom and as the isotopes have the same number of electrons it results in the fact that they exhibit similar chemical properties. Isotones refers to two nuclides which have the same number of neutrons, but different proton number. Isoelectronic species refers to the elements or ions that have an equal number of electrons. Isobars refer to the atoms of different elements with different atomic numbers but the same mass numbers. They have different chemical properties because they have different atomic numbers.