Periodic Table

2. Elements found along the staircase line between metals and non-metals are called __________.
4. shell The outermost energy level of an atom containing electrons is called the __________.
6. mass The average mass of an atom of an element is shown as its __________.
9. Protons have a positive electrical __________.
12. Elements found on the left side of the periodic table are generally classified as a __________.
13. Electrons have a __________ electrical charge.
14. A particle in the nucleus with no charge is a __________.
17. number The total number of protons and neutrons in an atom is called the __________.
18. A vertical arrangement of elements in the periodic table is called a __________.
21. symbol The one- or two-letter abbreviation used to represent an element is called its __________.
22. The rows that run across the periodic table are called __________.
24. Electrons are arranged around the nucleus in energy __________.
26. table The organised chart that displays all known elements is called the __________.
27. The columns that run up and down the periodic table are called __________.
30. A substance made from only one type of atom is called an __________.

1. Two or more atoms joined together form a __________.
3. A substance made from two or more different types of atoms chemically joined is called a __________.
5. Elements found on the right side of the periodic table are generally classified as a __________.
7. gases The group containing elements with full outer electron shells is called the __________.
8. number Elements are arranged in the periodic table based on their atomic __________.
10. The small particles that move around the nucleus are called __________.
11. Elements in the same group have the same number of __________ electrons.
15. The number of protons in an atom is called its atomic __________.
16. The centre of an atom containing protons and neutrons is called the __________.
19. levels The regions around the nucleus where electrons are found are called __________.
20. A particle in the nucleus with a positive charge is a __________.
23. A particle with a negative charge found outside the nucleus is an __________.
25. The first element on the periodic table is __________.
28. Atoms are usually electrically __________ because they have equal numbers of protons and electrons.
29. The number of occupied electron shells in an atom is shown by its __________ number.