Atoms, Elements and Compounds – Simple Molecules & Covalent Bonds
A covalent bond is formed when two atoms share a pair of electrons so that each atom achieves a noble‑gas electronic configuration. Think of it like two friends sharing a pizza slice – each gets a fair share and both are happy! 🍕
Below is a quick table showing how hydrogen and oxygen reach their noble‑gas states by sharing electrons to form water (H₂O). The table also illustrates the electron configuration of each atom before and after bonding.
| Atom | Before Bonding | After Bonding |
|---|---|---|
| Hydrogen (H) | \$1s^1\$ | \$1s^2\$ (like He) |
| Oxygen (O) | \$1s^2 2s^2 2p^4\$ | \$1s^2 2s^2 2p^6\$ (like Ne) |
In water, each hydrogen shares its single electron with one of the two electrons in oxygen’s outer shell, forming two covalent bonds. The result: H₂O, a stable molecule where every atom has a full valence shell.
Remember: When asked to explain a covalent bond, always mention the sharing of a pair of electrons and the goal of achieving a noble‑gas configuration. Use the electron configuration as evidence. For example, show that H goes from \$1s^1\$ to \$1s^2\$ and O from \$2p^4\$ to \$2p^6\$ when forming H₂O. ✏️
Tip 1: Use the “pizza slice” analogy to quickly illustrate sharing.
Tip 2: Practice drawing Lewis dot structures; they help visualise shared pairs.
Tip 3: Check the valence shell of each atom – if it’s full after bonding, you’re on the right track.