Explanation:
calcium ion is denoted as - Ca ²⁺
The number of electrons in a neutral atom of calcium = 20 , but since ,
it is charged atom ,
i.e. +2 , the number of electrons in calcium ion = 18 .
From , the question ,
The mass number = 41 ,
and
since ,
the mass number = number of protons + number of neutrons .
number of neutrons = mass number - number of protons
since ,
The number of protons for calcium ion = 20
number of neutrons = 41 - 20 = 21
Hence ,
number of neutrons = 21.
The population density is 47 people/km^2..
<em>Step 1</em>. Calculate the <em>surface area of Earth</em>.
<em>d</em> = 12 700 km; <em>r</em> = 6350 km
<em>A</em> = 4π<em>r</em>^2 = 4π × (6350 km)^2 = 5.067 × 10^8 km^2
<em>Step 2</em>. Calculate the <em>habitable surface area</em>.
Habitable area = 5.067 × 10^8 km^2 total × (30 km^2 habitable/100 km^2 total) = 1.520 × 10^8 km^2 habitable
<em>Step 3</em>. Calculate the <em>population density
</em>
Population density = 7.1 × 10^9 people/1.520 × 10^8 km^2 = 47 people/km^2
