By the end of the lesson the learner can define atomic number (Z) and mass number (A).
By the end of the lesson the learner can calculate the number of neutrons in an atom from A and Z.
By the end of the lesson the learner can write the electron arrangement of the first twenty elements.
Transcript
[0:00] Every element has its own identity card number called the atomic number, written with the letter Z.
[0:40] The atomic number tells you how many protons are in the nucleus, and in a neutral atom it also tells you the number of electrons.
[1:25] The mass number, written with the letter A, is the total of protons plus neutrons in the nucleus.
[2:10] To find neutrons, simply subtract the atomic number from the mass number. For chlorine, A is 35 and Z is 17, so neutrons equal 35 minus 17, which is 18.
[3:00] Electrons fill shells from the inside out. The first shell holds up to two electrons and the next shells hold up to eight, giving arrangements like 2.8.1 for sodium.
Plays from this package with no internet. The 🔊 Listen button also reads the lesson aloud.