Introduction to Atoms ions isotpes (1).ppt
- 1. Introduction to Atoms, Ions and Isotopes Honors Coordinated Science II Wheatley-Heckman
- 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? – Hint: If the mass number is a decimal, round it to the nearest whole number to calculate # of neutrons. • 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 elements that have the same number of protons, but a different number of neutrons.
- 10. 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.
- 11. 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)
- 12. Let’s Review! • ________ are charged atoms. – _________ ions have LOST electrons. – _________ ions have GAINED electrons. • An atom of Cu2+ has: – ________ protons – ________ neutrons – ________ electrons
- 13. More Review • ____________ are atoms of the same element that have different numbers of neutrons in the nucleus. • What does average atomic mass represent?