University:
Miami University
Course:
CHM 141 | College Chemistry
Academic year:

2023
Views:

460

Pages:

3
Author:

gewoekerdodx

Name: ______________________________________________ Period:______ Date:____________ Atomic Structure Guided Notes The Basic Structure of the Atom All atoms consist of a nucleus which contains two types of subatomic particles - protons and neutrons. The nucleus is surrounded by a cloud of electrons at varying energy levels. These subatomic particles are composed of even smaller particles known as quarks which came together after the Big Bang around 13.7 million years ago. The Nucleus The nucleus is held together by the "strong force," which binds the quarks together. This force found in the nucleus has sufficient strength to overcome the repulsive electrical force which aims to push like charges apart. Because this binding force varies from atom to atom, sometimes the nucleus decays into other elements as it breaks apart. Charged Subatomic Particles Protons and electrons are oppositely charged giving the atom an overall (net) charge of zero. The table below shows the charge and relative mass of each of the three particles found in the atom (the neutron is used as a point of comparison to find the relative mass of protons and electrons). Proton Neutron Electron Charge Positive No charge (neutral) Negative Relative Mass 0.9986 1 0.0005439 The Mass of an Atom: The majority of the mass of an atom is found in its nucleus. The protons and neutrons are approximately the same mass (with the proton being is slightly less), known as one atomic mass unit (AMU) or one Dalton. Electrons are much smaller than protons and neutrons, so much so, that they do not contribute much to the mass of an atom. Name: ______________________________________________ Period:______ Date:____________ Atomic Structure Guided Notes Atomic Number: The atomic number tells us how many protons it has. It is denoted by the letter ‘Z’. This number can be found under the entry for each element on the periodic table. Mass Number: The mass number provides information about the number of protons and neutrons contained in the atoms nucleus. It is denoted by the letter ‘A’. To find the number of neutrons in any given element, the atomic number (or number of protons) is subtracted from the mass number. An example: A lithium atom has the atomic number (Z) of 3, and the atomic mass (A) of 6.94 (round it up to 7!). Therefore lithium contains three protons (found from Z), and three electrons (as the number of protons must be equal to the number of electrons in order for the atom to be neutral). Lithium also contains four neutrons (7 – 3 = 4). Practice: Use the periodic table from your guided notes (page 3) to complete the table below: Number of protons Number of electrons Number of neutrons Hydrogen 1 1 0 Fluorine 9 9 10 Calcium 20 20 20 Iodine 53 53 74 Gold 79 79 118 Name: ______________________________________________ Period:______ Date:____________ Atomic Structure Guided Notes