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Ch. 11 Section 2

Ch. 11 Section 2. The Atom. Vocabulary T o Know. Proton- subatomic particle that has a positive charge and that is found in the nucleus Atomic mass unit- a unit of mass that describes the mass of an atom or molecule

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Ch. 11 Section 2

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  1. Ch. 11 Section 2 The Atom

  2. Vocabulary To Know • Proton- subatomic particle that has a positive charge and that is found in the nucleus • Atomic mass unit- a unit of mass that describes the mass of an atom or molecule • Neutron- a subatomic particle that has no charge and that is found in the nucleus of an atom • Atomic number- the number of protons in the nucleus of an atom

  3. Vocabulary To Know Cont.. • Isotope- an atom that has the same number of protons as other atoms of the same elements do but that has a different number of neutrons • Mass number- the sum of the numbers of protons and neutrons in the nucleus of an atom • Atomic mass- the mass of an atom expressed in atomic mass units

  4. What is an Atom Made of?- Inside the Nucleus • The nucleus contains protons and neutrons. • Since the particles of an atom are so small scientists came up with a new SI unit of measurement know as AMU. • The atomic mass unit of proton is 1. • The atomic mass unit of a neutron is 1. • Protons and neutrons are the most massive particles in an atom.

  5. What is an Atom Made of?- Outside the Nucleus • Electrons are negatively charged particles in atoms. • Electrons are located outside of the nucleus on the electron cloud. • The mass of an electron is so small that is has no AMU.

  6. ION • An atom has an overall charge of zero. • When the protons and neutrons are not equal in an atom, the atom becomes a charged particle known as an ion. • An atom that loses one or more electrons becomes a positively- charged ion. • An atom that gains one or more electrons becomes a negatively- charged ion.

  7. How do Atoms of Different Elements Differ? • Since there are more than 110 different elements, they all differ by the number of protons, neutrons, and electrons that they have. • The number of protons in the nucleus of an atom is the atomic number. • All atoms of the same element have the same atomic number.

  8. Isotopes • Isotopes are atoms that have the same number of protons but have different number of neutrons. • Atoms that are isotopes of each other are always the same element since they have the same number of protons. • They have different number of neutrons, however which gives them different masses. • You can identify each isotope of an element by its mass number. • The mass number is the sum of the number of protons and neutrons in the nucleus of an atom.

  9. Calculating the Mass of an Element • Most elements contain a mixture of two or more isotopes. • The atomic mass of an element is the weighted average of the masses of all the naturally occurring isotopes of that element. • The atomic mass is the mass of an atom expressed in atomic mass units.

  10. Forces in Atoms • Four basic forces are at work every where, even within the atom. • They are: gravitational force, electromagnetic force, strong force, and weak force. • These forces work together to give an atom its structure and properties.

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