Answer:
The speed of light, c, equals the wavelength, λ (pronounced lambda), times the frequency, ν, (pronounced noo).
c=λν
c is a constant. It is usually given as 3.00×108 m/s or 3.00×1010 cm/s rounded to three significant figures.❤
Isotopes are defined as atoms of same element with different mass number and same atomic number.
Here, atomic number is equal to number of protons and number of electrons, it is denoted by symbol Z thus,

and, mass number is equal to sum of number of protons and neutrons, it is denoted by symbol A thus,

The three isotopes of tin are given, Sn-116, Sn-120 and Sn-126, mass number for these three isotopes is 116, 120 and 126 respectively. Since, they are isotopes thus, atomic number remains the same that is 50.
Since,
thus, number of protons and electrons will be 50.
For Sn-116,

Or,

Or,

For Sn-120,

For Sn-126,

Therefore, mass number, number of protons, electrons and neutrons in all three isotopes are:
Sn-116:
Mass number= 116
Protons=50
neutrons=66
electrons=50
Sn-120:
Protons=50
neutrons=70
electrons=50
Sn-126:
Protons=50
neutrons=76
electrons=50
Answer:
the packing efficiency is 52.36%
Explanation:
Given the data in the question;
simple cubic unit cell that contains one atom with a metallic radius of 175 pm;
we know that;
Edge length of Simple cubic (a) is related to radius of atom (r) as follows;
a = 2r
since radius r = 175 pm
we substitute
a = 2 × 175 pm
a = 350 pm
Now we get the volume unit;
Volume of unit cell = a³ = ( 350 pm ) = 42875000 pm³
Next we get Volume of sphere;
Volume of Sphere =
πr³
Volume occupied by 1 atom =
× π × ( 175 pm )³
=
× π × 5359375 pm³
= 22449297.5 pm³
Now, the packing efficiency = ( Volume occupied by 1 atom / Volume of unit cell ) × 100
we substitute;
packing efficiency = ( 22449297.5 pm³ / 42875000 pm³ ) × 100
= 0.523598 × 100
= 52.36%
Therefore, the packing efficiency is 52.36%
I’m sorry if I wasted your time but I think it’s alkali metals but I’m
Not sure