To determine the number of species having a higher first ionization energy than calcium (Ca) from the given list (Ga, Ge, Br, Se, Kr, As, K), we will follow these steps:
### Step 1: Understand Ionization Energy
Ionization energy is the energy required to remove the outermost electron from an atom. Generally, ionization energy increases across a period (from left to right) and decreases down a group (from top to bottom) in the periodic table.
### Step 2: Identify the Position of Calcium
Calcium (Ca) is located in Group 2 (alkaline earth metals) and Period 4 of the periodic table. The first ionization energy of calcium is approximately 590 kJ/mol.
### Step 3: List the Elements and Their Positions
We need to identify the positions of the other elements in the periodic table:
- Ga (Gallium) - Group 13, Period 4
- Ge (Germanium) - Group 14, Period 4
- Br (Bromine) - Group 17, Period 4
- Se (Selenium) - Group 16, Period 4
- Kr (Krypton) - Group 18, Period 4
- As (Arsenic) - Group 15, Period 4
- K (Potassium) - Group 1, Period 4
### Step 4: Compare Ionization Energies
Now we will compare the first ionization energies of these elements with that of calcium:
- **K (Potassium)**: Lower than Ca (1st group element)
- **Ga (Gallium)**: Lower than Ca
- **Ge (Germanium)**: Lower than Ca
- **As (Arsenic)**: Higher than Ca
- **Se (Selenium)**: Higher than Ca
- **Br (Bromine)**: Higher than Ca
- **Kr (Krypton)**: Higher than Ca (noble gas, highest ionization energy)
### Step 5: Count the Elements with Higher Ionization Energy
From the comparison:
- Higher than Ca: As, Se, Br, Kr
- Not higher than Ca: K, Ga, Ge
Thus, the elements with higher first ionization energy than calcium are:
1. As
2. Se
3. Br
4. Kr
### Conclusion
The total number of species having higher first ionization energy than calcium is **4**.
---
