Atoms-Elements

What are elements? There are many different types of atoms, called elements. Hydrogen, carbon, oxygen, sodium, and chlorine are a few different elements. The number of protons an atom has determines which element it is.

The simplest type of atom, which only has one proton, is the element hydrogen. Unlike every other element, hydrogen doesn't have any neutrons. The element oxygen is more complex; oxygen atoms have 8 protons. Your body is made of a whole lot of atoms of these two elements (hydrogen and oxygen)!

Atoms in their basic "elemental" forms have no "net" charge. That is, they have the same number of (negatively charged) electrons (e-) and (positively charged) protons (p+). So, hydrogen atoms have one electron. Oxygen atoms have 8 electrons.

The elements we have discovered (so far!) are shown in Periodic Tables like this one. Elements in Periodic tables are ordered by "atomic number," which is the number of protons the element has. The atomic number/number of protons is shown in the top right corner of each box for each element. For example, as you can see in the Periodic Table, the element Sodium (Na) has 11 protons.

Names of elements. Different elements (types of atoms) are abbreviated with one or two letters. The first letter is always capitalized.

For example:

Hydrogen is abbreviated as "H".
Helium is "He". (They couldn't use just "H", since it would be confused with hydrogen.)
Carbon is "C".
Chlorine is "Cl". (They couldn't use just "C", since it would be confused with carbon.)
Oxygen is "O".

Ions of elements: Sometimes elements gain or lose one or more electrons. Because the atoms no longer have the same number of protons (+) and electrons (-), they have an electric charge. Atoms that have lost or gained electrons are called ions.

One example of an ion is a hydrogen (H) atom that has lost an electron. It now has one proton (p+) but no electrons. So, the hydrogen ion has a positive charge. A hydrogen ion is written as H+.

The "+" sign means that it has a "net" positive charge, or there are more (positively-charged) protons than (negatively-charged) electrons.

Another example of an ion is a Fluorine (F) atom that has gained an electron (e-). It now has one more electron than protons (p+), so it has a negative charge. A Fluorine ion (called Fluoride) is written as Fl-.

The "-" sign means that it has a "net" negative charge, or there are more (negatively-charged) electrons than (positively-charged) protons.

Q0.6: The element Clorine (Cl) has 17 protons. Which of the following would be a Chlorine ion?

a) a Cl atom with 17 protons & 17 electrons

b) a Cl atom with 17 protons & 18 electrons

c) a Cl atom with 18 protons & 17 electrons

d) a Cl atom with 18 protons & 18 electrons

Right! The element Chlorine always has 17 protons (that's how you know it's Chlorine). A Chlorine ion has a different number of electrons than protons. So, a Cl atom with 17 protons and 18 electrons is a Cl ion.

Well, the element Chlorine always has 17 protons (that's how you know it's Chlorine). A Chlorine ion has a different number of electrons than protons. So, a Cl atom with 17 protons and 18 electrons is a Cl ion.

Q1: An atom of the element Clorine (Cl) has a total of 18 electrons. How should this Chlorine ion be represented in writing?

a) Cl

b) Cl+

c) Cl-

d) How should I know?

You are correct! Looking at the Periodic Table, you can see that Chlorine's atomic number is 17. This means that it has 17 protons. Since this Chlorine atom has 18 electrons, it has one more negatively-charged particle than positively-charged particle. Since it has a "net" negative charge, we'd write it as Cl-.

Well, if you look at the Periodic Table, you can see that Chlorine's atomic number is 17. This means that it has 17 protons. Since this Chlorine atom has 18 electrons, it has one more negatively-charged particle than positively-charged particle. Since it has a "net" negative charge, we'd write it as Cl-.

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Elements

Table of Contents: Elements unit