Forming ions
An electrically charged The smallest part of an element that can exist. is called an Electrically charged particle, formed when an atom or molecule gains or loses electrons.. Ions are formed when atoms lose or gain negatively charged Subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons..
The number of electrons lost or gained determines the charge of the ion:
- the number lost is the same as the number of positive charges
- the number gained is the same as the number of negative charges
The number of Subatomic particle with a positive charge and a relative mass of 1. The relative charge of a proton is +1. and Uncharged subatomic particle, with a mass of 1 relative to a proton. The relative charge of a neutron is 0. in an ion is the same as in the atom, and is worked out in the same way.
Learn more on ionic bonding in this podcast.
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Forming positive ions
Positive ions are called An atom or group of atoms that have lost electrons and become positively charged. Most cations are formed from metals..
Sodium is in group 1. A sodium atom has one electron in its outer shell. The atom is more stable if it has a full outer shell.
A sodium atom can lose its outer electron. It will still have 11 positive protons but only 10 negative electrons. So, the overall charge is +1.
A positive sign is added to the symbol for sodium, Na+. Ions with greater charge include a number in their symbol, for example Al3+ (which has three positive charges).
Question
Magnesium is in group 2.
- How many electrons are in the outer shell of a magnesium atom?
- What is the charge of a magnesium ion and what is its symbol?
- a magnesium atom has 2 electrons in its outer shell
- a magnesium atom can lose both outer electrons, so a magnesium ion has a charge of +2 and its symbol is Mg2+
Question
The atomic number of lithium is 3. Its mass number is 7. How many protons, neutrons and electrons are there in a lithium ion?
- The number of protons = atomic number. So the number of protons is 3.
- The number of neutrons = mass number - atomic number. So the number of neutrons is 7 - 3 = 4.
- Lithium has 1 electron in its outer shell because it is in group 1. Or you can work out its The order electrons are arranged into between different energy levels., which is 2.1 (number of electrons = atomic number). This means that it forms an ion by losing one electron. An Li+ ion has 2 electrons.
Explaining reactivity in group 1
Going down A vertical column in the periodic table containing elements with similar chemical properties. 1, the outer electron is further away from the positive The central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. The plural of nucleus is nuclei.. It is also shielded from the nucleus by more electron shells. Because of this, it becomes easier to lose the outer electron, so the A substance made of one type of atom only. get more reactive moving down the group.
The A measure of how vigorously a substance will react. The more reactive it is, the greater its reactivity and the more vigorous its reactions will be. depends on the number of electrons and therefore the The number of protons in the nucleus of an atom. Also called the proton number. of the element.