Protons and electrons

Remember: The atomic number of an element is the number of ________ in each atom.

• electrons

• nuclei

• neutrons

• protons

Apply: The element hydrogen is first on the periodic table, so its atomic number is 1. This means that every hydrogen atom must have:

• one proton

• one electron

• one neutron

• I'm not sure

Apply: An atom of gold has 79 protons. What is the atomic number of gold?

• Au

• 6

• 79

• 197

• I'm not sure

Select two statements that correctly complete the sentence: An atom is electrically neutral when:

• the number of positively charged subatomic particles equals the number of negatively charged subatomic particles

• the number of protons equals the number of neutrons

• the number of protons equals the number of electrons

• the only charged particles within atoms are protons (positive) and electrons (negative) so these must balance each other. Neutrons are electrically neutral so do not affect the overall charge of the atom.

• it has no charged subatomic particles

An atom with one proton and one electron is electrically neutral. This means that the charge of an electron must be:

• half the size

• the same size

• double the size

• I'm not sure

Apply: An electrically neutral atom of lithium has 3 protons. How many electrons must it have?

• 1

• 3

• 6

• More information is needed, I'm not sure

Apply: An electrically neutral atom has 5 electrons. Which element must the atom be? Hint: Refer to the table of the first 6 elements you completed above.

• Hydrogen

• Boron

• Carbon

• More information is needed, I'm not sure

Evaluate: Summarize what you think are the three most important ideas from today's lesson.