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Introduction to Atoms, Ions and Isotopes

Introduction to Atoms, Ions and Isotopes. What are atoms?. The atom is a basic unit of matter that consists of a dense, central nucleus surrounded by a cloud of negatively charged electrons.

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Introduction to Atoms, Ions and Isotopes

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  1. Introduction to Atoms, Ions and Isotopes

  2. What are atoms? • The atom is a basic unit of matter that consists of a dense, central nucleus surrounded by a cloud of negatively charged electrons. • While all atoms have protons, neutrons and electrons, atoms of different elements have different numbers of these.

  3. Atoms • Each element on the periodic table has an atomic number, which tells how many protons an atom of that element has. • Each element also has an mass number. • Mass number = # of Protons + # of Neutrons

  4. Electrons • Neutral atoms have the same number of electrons (negative charge) as they do protons (positive charge). • # of electrons = atomic number • ONLY IN NEUTRAL ATOMS

  5. Let’s Practice! • Find Boron on the periodic table. • How many protons does an atom of Boron have? • How many neutrons? • Assume the mass number is 11 • How many electrons?

  6. Ions • An atom or small molecule with an overall positive or negative charge due to an imbalance of protons and electrons. • # of protons does not change • # of electrons changes. • Positive charge = loss of electrons • Negative charge = gain of electron

  7. Ions Continued… • Ions are represented by a superscript charge on the element symbol. • Examples: F-, Mg2+, Al3+ Practice: • How many protons, neutrons, and electrons does Al3+ have?

  8. Isotopes • All neutral atoms of the same element have the same number of protons, and therefore the same number of electrons. • The number of neutrons CAN vary. • Isotopes: atoms of an element that have the same number of protons, but a different number of neutrons.

  9. Average Atomic Mass • The mass shown on your periodic table as a decimal is the average atomic mass. • Average mass of all isotopes of an atom in nature.

  10. Example: Lithium • 2 Isotopes are found in nature: Lithium-6 and Lithium-7 (Lithium-8 is radioactive and quickly decays) • Atomic mass is listed as 6.94. • How is that possible? • 94% of Li atoms have an atomic mass of 7, and 6% have an atomic mass of 6. • Avg. Atomic Mass = (7 x .94) + (6 x .06)

  11. Let’s Review! • ________ are charged atoms. • _________ ions have LOST electrons. • _________ ions have GAINED electrons. • An atom of Cu2+ with mass number 63 has: • ________ protons • ________ neutrons • ________ electrons

  12. More Review • ____________ are atoms of the same element that have different numbers of neutrons in the nucleus. • What does average atomic mass represent?

  13. Complete Atomic Structure WS #1 Front and Back Hint: Chromium-52 means Chromium with a mass number of 52. 26Fe means iron with atomic number 26.

  14. Related Book Work • Read section 5.1 • Pg. 134-143 • Answer the following questions on page 162 1-3, 6, 7, 29, 31, 32, 38, 65, 71-76.

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