Across
- 1. A period is a horizontal row of the periodic table. There are seven periods in the table, with each one beginning at the far left. A new period begins when a new principal energy level begins filling with electrons. Period 1 has only two elements (hydrogen and helium), while periods 2 and 3 have 8 elements.
- 4. A subatomic particle that has no charge and that is located in the nucleus of an atom
- 9. The number of protons in the nucleus of an atom; the atomic number is the same for all atoms of an element
Down
- 1. A subatomic particle that has a positive charge and that is located in the nucleus of an atom; the number of protons in the nucleus is the atomic number, which determines the identity of an element
- 2. A subatomic particle that has a negative charge
- 3. Mass number is the sum of the numbers and protons and neutrons present in the nucleus of an atom
- 5. A substance that cannot be separated or broken into simpler substances by chemical means
- 6. table An arrangement of the elements in order of their atomic numbers such that elements with similar properties fall in the same column, or group
- 7. The smallest unit of an element that maintains the properties of that element
- 8. In chemistry, a column in the periodic table of the chemical elements