Atoms

Question 1

Which of the following is the radius of an atom

a) 1 x 10 ^-10 m
b) 1 x 10^-12 m
c) 0.1 nano meters

Answer 1

A and c are the same thing

Question 2

Nucleus of an atoms

Answer 2

• middle of an atom
• contains both protons and neutrons
• radius of nucleus is 1 x 10^-14
• positive charge due to protons
• whole mass of an atom is concentrated in the nucleus

Question 3

The electrons

Answer 3

• move around nucleus in electron shells
• negatively charged and tiny but cover a lot of space
• Volume of their orbits determine the size of the atom
• electrons have virtually no mass

Question 4

Proton, neutron and electrons relative mass and charge

Answer 4

Proton 1 +1
Neutron 1 0
Electron very small -1

Question 5

Atoms have no charge overall so they are ———-
Why ?

Answer 5

neutral ( unlike ions )
Because they have same number of protons as electrons
Charge of proton and electron is same size but opposite so charges cancel out

Question 6

What happens in an ion ?

Answer 6

number of protons does not equal to number of electrons so it has an overall charge. Example an ion with -2 charge has two more electrons than protons

Question 7

nuclear symbol tells you mass number and atomic number.
What does atomic and mass number tell you ?

Answer 7

Mass number ( top one ) = tells you total number of protons and neutrons
atomic number = tells you how many protons

Neutrons = mn - an