Physical change
Giddy Up!!!!!
Answer:
3
Explanation:
Applying,
= R/R'............... Equation 1
Where n' = number of halflives that have passed, R = Original atom of the substance, R' = atom of the substance left after decay.
From the question,
Given: R = 40 atoms, R' = 5 atoms
Substitute these values into equation 1
= 40/5
= 8
= 2³
Equation the base,
n' = 3
Answer and Explanation:
The basic unit which are that are important in chemistry are meter, kilogram ,mol,
Candela which is the unit of luminous of intensity is not so important in physics
(a) SI unit of length is meter (m)
(b) Si unit of volume is 
(c) Si unit of mass is kilogram (kg)
(d) SI unit of time is second (s)
(e) SI unit of temperature is kelvin (K)