In class 9 chemistry, you will typically learn about the basic concepts of the periodic table and elements. While the specific curriculum may vary, here are some important elements and their atomic numbers that you should be familiar with:
- Hydrogen (H) - Atomic number 1
- Helium (He) - Atomic number 2
- Carbon (C) - Atomic number 6
- Oxygen (O) - Atomic number 8
- Nitrogen (N) - Atomic number 7
- Sodium (Na) - Atomic number 11
- Magnesium (Mg) - Atomic number 12
- Aluminum (Al) - Atomic number 13
- Chlorine (Cl) - Atomic number 17
- Potassium (K) - Atomic number 19
- Calcium (Ca) - Atomic number 20
- Iron (Fe) - Atomic number 26
- Copper (Cu) - Atomic number 29
- Zinc (Zn) - Atomic number 30
These are some commonly studied elements that will help you understand the periodic table and its basic trends. Additionally, it's important to understand the concept of atomic mass, which is the average mass of the isotopes of an element. However, you may not need to memorize specific atomic mass numbers in class 9.
Please keep in mind that the specific curriculum may vary, so it's best to consult your teacher or refer to your textbook for the precise elements and concepts you are expected to learn in your class.