CC6 Flashcards
What do molecular substances contain?
Molecular substances contain groups of atoms that are held together by covalent bonds.
How are the number of atoms of each element shown?
The number of atoms of each element bonded together in a simple molecule is shown by its molecular formula.
What are covalent bonds formed between and how are they formed?
Covalent bonds are usually formed between non-metal atoms and are produced by sharing pairs of electrons. They can use the shared electrons to complete their outer electron shells, making them bonded.
What is the dot and cross diagram?
The dot and cross diagram is a 2d diagram that shows how covalent bonds are formed. Counting the shared electrons, each atom now has a complete outer shell of electrons. Dots show electrons from one atom and crosses show electrons from the other atom.
What are double bonds (double covalent bonds)?
Sometimes, atoms share more than one pair of electrons to fill their outer shells. They may share more than one atom of that element to fill the outer shells of all of the atoms, forming double bonds.
What are the atoms in molecules held together by?
They are held together by strong electrostatic forces of attraction between the positive nuclei and the negative electrons in the bonded atoms.
What are some models used to represent atoms and molecules?
- Molecular formula (CH⁴)
- Full dot and cross diagram (all shells)
- Dot and cross diagram (outer shell only)
- 3D space filling (3d diagram of balls representing atoms)
- Ball and stick model (3d diagram of balls representing atoms and sticks representing covalent bonds)
- Structural formula (2d model with stick bonds)
What is meant by the ‘valency’ of an element?
The valency of an element is the number of covalent bonds formed by an atom, or the number of electrons needed to obtain a complete outer shell.
