Hydrogen is the first element - it has atomic number 1. This means that a hydrogen atom has one proton and one electron.
The most common isotope of hydrogen is hydrogen-1, which makes up over 99% of all of the hydrogen atoms on Earth. Hydrogen-1 has no neutrons. This means that most hydrogen atoms consist of just a single electron orbiting around a single proton.
A hydrogen atom.
A hydrogen atom's electron is in the first shell, which has a capacity of 2. Therefore, the shell is half-full. This means that there are two ways that it can get a full outer shell: it can either lose an electron or it can gain an electron.
A hydrogen atom can lose an electron, leaving it with no electrons. Technically, having no electrons is not quite the same thing as having a full outer shell, but we usually think of it as a full outer shell.
When the electron is lost, all that is left behind is a single proton. Even though it is just a proton, we still call it a hydrogen ion. Since it has a relative charge of +1, its formula is H+.
The formation of a hydrogen ion from a hydrogen atom is shown below:
A hydrogen atom is made of one proton and one electron. It can lose the electron to form an H+ ion, which is actually just a proton.
A hydrogen atom can also get a full outer shell by gaining an electron, resulting in it having two electrons.
Since the ion formed has two electrons and one proton, it has a relative charge of -1. Therefore its formula is H-. This is called a hydride ion. (Remember that for negative ions the ending of the name of the element is replaced with -ide).
The formation of a hydride ion is shown below:
A hydrogen atom can gain an electron to get a full outer shell. When it does this it forms a hydride ion, which has a charge of -1. Its formula is H-.
Although hydrogen ions (H+) and hydride ions (H-) both occur naturally, hydrogen ions are much more common.
Flashcards help you memorise information quickly. Copy each question onto its own flashcard and then write the answer on the other side. Testing yourself on these regularly will enable you to learn much more quickly than just reading and making notes.
What is the name of the positive ion that hydrogen forms? What is its formula? What is unusual about it?
What is the name of the negative ion that hydrogen forms? What is its formula?
Which ion of hydrogen is most common?
3.6.6 - Ions of Transition Elements
3.6.4 - Ions of Group 1-7 Elements
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