Atoms And Molecules

Atoms and Molecules

Atoms • Atoms are the smallest particles of matter • Matter is anything that takes up space and has mass • Atoms consists of three types of parts: protons, neutrons and electrons • The centre of an atom is called the nucleus. In that nucleus we find the protons and neutrons

• The electrons are found in orbits outside the nucleus • Each type of atom has a special number of protons. This is what makes the difference between 2 types of atoms or elements • Example: Page 206-207 of textbook- find Aluminum and Calcium

• Aluminum has the chemical symbol Al and contains 13 protons, which is what makes it 13th in the periodic table • Calcium has 20 protons and is 20th in the table • The different number of protons will change the properties of these two different metals

• Protons are positively charged and have a mass of 1 amu • Amu stand for atomic mass unit • Neutrons do not carry any charge and also have a mass of 1 amu

• Electrons have a negative charge and almost no mass. We describe this type of mass as negligible

• Most matter is electronically neutral since protons carry a positive charge and electrons a negative one, they cancel each other out • Atoms join together in different combinations to form what we call molecules