Chemical formula of compounds Flashcards
What does the chemical formula for a compound show?
The chemical formula for a compound shows:
* the symbols for each element in the compoun
* the number of atoms of each element in a unit of the compound
What is an atom?
The smallest part of an element that can exist.
What is a covalent bond?
A bond formed between two atoms, where electrons are shared, is called a covalent bond. This is to achieve a full outershell of electrons.
What is an electron?
A subatomic particle, with a negative charge and a neglegible mass relative to protons and neutrons.
What do covalent compounds usually form from?
Covalent bonds usually form between non-metal elements.
What are covalent compounds held together by?
They are held together by covalent bonds.
What compounds are all covalent?
All compounds that exist as molecules are covalent.
Give the names of some covalent compounds and their chemical formula:
- Ammonia - NH3
- Carbon Dioxide - CO2
- Methane- CH4
- Sulfur dioxide - SO2
- Water - H20
What is a subscript?
A letter or number written below the line.
What does the subscript show?
The subscript numbers in the formulae show how many atoms of that element appear in the molecule.
What is an ionic bond?
- A bond formed between two atoms when an electron is transferred from atom to another is called an ionic bond.
- They form a positive-negative ion pair.
What are ionic compounds made up of?
Ionic compounds are made up of atoms joined together by ionic bonds.
When does an ionic compound occur?
An ionic compound occurs when a negative ion joins with a positive electron.
What is a negative ion?
An atom that has gained an electron.
What is a positive ion?
An atom that has lost an electron.
