First, we need to identify all the chemical elements with atomic number less than 5. Here are the elements in increasing order of their atomic numbers:
1. Hydrogen (H) with an atomic mass of 1.008 u.
2. Helium (He) with an atomic mass of 4.002602 u.
3. Lithium (Li) with an atomic mass of 6.94 u.
4. Beryllium (Be) with an atomic mass of 9.0122 u.
Next, we check which of these elements have an atomic mass greater than 8.4 u.
- Hydrogen (H) has an atomic mass of 1.008 u, which is not greater than 8.4 u.
- Helium (He) has an atomic mass of 4.002602 u, which is not greater than 8.4 u.
- Lithium (Li) has an atomic mass of 6.94 u, which is not greater than 8.4 u.
- Beryllium (Be) has an atomic mass of 9.0122 u, which is greater than 8.4 u.
Therefore, the only element that meets both criteria — atomic number less than 5 and atomic mass greater than 8.4 u — is Beryllium (Be).
The symbol for Beryllium is Be.
