Electronic Arrangement: Remember 2, 8, 8!!! A worksheet illustrating the electronic structure of the first 20 elements, highlighting atomic numbers and electron configurations.

Problem Analysis:

The task involves drawing the electronic arrangements (electron configurations) of the first 20 elements in the periodic table. The goal is to fill in the electronic structures for the given elements: Hydrogen (H), Helium (He), Lithium (Li), and Beryllium (Be). The electronic arrangement should follow the rule of filling electron shells based on the atomic number (proton number).

Key Concepts:

1. Atomic Number: The number of protons in the nucleus of an atom, which determines the element.
2. Electron Configuration: The arrangement of electrons in different energy levels (shells) around the nucleus.
3. Shells and Subshells:
- The first shell can hold up to 2 electrons.
- The second shell can hold up to 8 electrons.
- The third shell can hold up to 8 electrons (for the first 20 elements).
4. Rule of 2, 8, 8: Electrons fill the shells in the order of 2 (first shell), 8 (second shell), and 8 (third shell).

Solution:

#### 1. Hydrogen (H)
- Atomic Number: 1
- Electronic Structure: Hydrogen has 1 electron. This electron goes into the first shell (K-shell), which can hold up to 2 electrons.
- Configuration: 1s¹
- Diagram: A single circle representing the nucleus, with one dot outside representing the electron.

```
H
Atomic Number = 1
Electronic Structure = 1s¹
```

#### 2. Helium (He)
- Atomic Number: 2
- Electronic Structure: Helium has 2 electrons. Both electrons go into the first shell (K-shell), which can hold up to 2 electrons.
- Configuration: 1s²
- Diagram: A single circle representing the nucleus, with two dots outside representing the electrons.

```
He
Atomic Number = 2
Electronic Structure = 1s²
```

#### 3. Lithium (Li)
- Atomic Number: 3
- Electronic Structure: Lithium has 3 electrons. The first shell (K-shell) can hold 2 electrons, so the remaining 1 electron goes into the second shell (L-shell).
- Configuration: 1s² 2s¹
- Diagram: A single circle representing the nucleus, with two dots in the first shell and one dot in the second shell.

```
Li
Atomic Number = 3
Electronic Structure = 1s² 2s¹
```

#### 4. Beryllium (Be)
- Atomic Number: 4
- Electronic Structure: Beryllium has 4 electrons. The first shell (K-shell) can hold 2 electrons, so the remaining 2 electrons go into the second shell (L-shell).
- Configuration: 1s² 2s²
- Diagram: A single circle representing the nucleus, with two dots in the first shell and two dots in the second shell.

```
Be
Atomic Number = 4
Electronic Structure = 1s² 2s²
```

Final Answer:

```
Hydrogen (H)
Atomic Number = 1
Electronic Structure = 1s¹

Helium (He)
Atomic Number = 2
Electronic Structure = 1s²

Lithium (Li)
Atomic Number = 3
Electronic Structure = 1s² 2s¹

Beryllium (Be)
Atomic Number = 4
Electronic Structure = 1s² 2s²
```

$$
\boxed{
\text{Hydrogen (H): 1s¹, Helium (He): 1s², Lithium (Li): 1s² 2s¹, Beryllium (Be): 1s² 2s²}
}
$$