We have spent a great deal of time discussing atoms but what do they look like? Atoms are “particles” that are comprised of smaller particles called “subatomic particles”. Electrons, protons, and neutrons are subatomic particles.
Protons are positively charged particles. Protons have a relative mass of 1. Protons are located in the nucleus of the atom. Protons are significant because the number of protons in an atom determines what an atom is. - For example, any atom with one proton is a hydrogen atom. Any atom with 29 protons is a copper atom.
The atomic number of an element indicates the number of protons in one atom of that element.
Inside the Atom - Protons Identify the element: 37 protons 48 protons 105 protons
Inside the Atom - Protons
Inside the Atom- Electrons Electrons are negatively charged particles. Electrons have a relative mass of 1/2000 of a proton. Electrons travel in regions of space around the nucleus of the atom.
Inside the Atom- Neutrons Neutrons are neutral particles. Neutrons are neither positively nor negatively charged. Like protons, neutrons have a relative mass of 1. Like protons, neutrons are found in the nucleus of the atom.
Atomic Number The atomic number tells us the number of protons in one atom of the element. The atomic number also tells us the number of electrons in one atom of an element. The number of electrons is equal to the number of protons when stable. Example: the atomic number of calcium is 20 therefore the number of protons is 20 and the number of electrons is also 20.
The atomic mass tells us the total number of protons and neutrons in one atom of the element. Therefore, if we know the atomic number and the atomic mass we can determine the number of neutrons. number of neutrons = atomic mass - atomic # Example: the atomic number of calcium is 20 and the atomic mass is 40. Therefore, the number of neutrons is 40-20 = 20.
Sample Questions
Sample Questions Sodium 11 11 12 Selenium 34 34 45 Fluorine 9 9 10 Helium 2 2 2
Standard Atomic Notation Scientists use a special system to communicate information about any atom. This system is known as the standard atomic notation. This system represents the numbers of subatomic particles. Examples: 36Cl 23Na 17 11 The top number is the atomic mass and the bottom number is the atomic number.
Standard Atomic Notation 36CL 36 is the atomic mass, 17 is the atomic 17 number. The number of protons is 17, the number of electrons is 17 and the number of neutrons is 19. 23Na 23 is the atomic mass, 11 is the atomic 11 number. The number of protons is 11, the number of electrons is 11 and the number of neutrons is 12.
Homework
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