Answer: The number 4 indicates 4 electrons.
Explanation: We are given an electronic configuration, which is:

Here,
- The letters denote the sub-shells of an element.
- The numbers written before the letters which are 1, 2 and 2 represents the Principle Quantum Number and these represents the energy level of the sub-shells.
- The number which are written in the superscripts which are 2, 2 and 4 denotes the electrons which are present in the sub-shell.
Hence, 4 indicates 4 electrons present in 2p sub-shell.
Answer: A. Is decomposition
B. Is synthesis where Na combines with Cl to form NaCl
C. Is single displacement or replacement. Mg displaces Cu.
Explanation:
Light bulb -it produces heat and light
toaster - it produces heat and the metal strips glow producing light
Explanation:
it helps to make juices.
It helps to make concentrated acid into dilute acid.