1. Unit 3
Atomic structure

2. Element – the simplest form of matter with a unique set of properties
Element – the simplest form of matter with a unique set of properties. Elements cannot be broken down into simpler substances
All elements are listed on the Periodic Table

3. Atom – the smallest part of an element that retains the properties of that element in a chemical reaction
Elements are made of atoms

4. Proton – a small positively charged particle found in the nucleus of an atom. It has a mass of 1 amu
The number of protons an atom contains determines the element

5. Neutron – a small uncharged (neutral) particle found in the nucleus of an atom. It has a mass of 1 amu
Neutrons serve as “the glue” that help keep the protons together in the nucleus

6. Electrons– a tiny negatively charged particle that orbits the nucleus in energy levels. It has essentially no mass (0 amu).
Electrons help atoms combine with other atoms in chemical bonds

7. Ion – An electrically charged atom
Ion – An electrically charged atom. An atom is electrically neutral, meaning it has an equal number of protons (+) and electrons (-). An atom that loses electrons becomes a positive ion An atom that gains electrons becomes a negative ion

8. Nucleus – the dense, positively charged center of an atom
Nucleus – the dense, positively charged center of an atom. It is made of protons and neutrons. It contains ALL of the atom’s mass

9. Atomic Number – the number of protons in an atom
Atomic Number – the number of protons in an atom. Each element is defined by its atomic number

10. Mass Number – the mass of an atom
Mass Number – the mass of an atom. The mass number is the sum of the protons and neutrons.
Units: atomic mass units (amu)

11. Isotope – one of two or more atoms that have the same atomic number (number of protons), but different numbers of neutrons.
Hydrogen-1
Hydrogen-2
Hydrogen-3

12. Atomic Mass – the average of all isotopes of an element
Atomic Mass – the average of all isotopes of an element. The atomic mass is listed on the Periodic Table

13. Chemical Reaction – the process in which two or more substances are combined and a new substance is created.
Oxygen Hydrogen  Water

14. Chemical Reactivity – the property of an element that describes how likely it is to combine with other elements. Reactive elements have an unstable number of electrons and will gain or lose electrons to achieve a more stable configuration
Chemically Reactive
Stable (full valence shell)

15. An atom’s chemical stability is determined by its valence electrons.
Chemical Stability – the opposite of chemically reactive. Stable elements have a full valence shell and do not combine with other elements.
Chemically Reactive
Stable (full valence shell)
An atom’s chemical stability is determined by its valence electrons.
Full valence shell = chemically stable
Not full = chemically reactive (unstable)

16. Period – Each row of the Periodic Table. There are seven periods
Period – Each row of the Periodic Table. There are seven periods. The period number represents the number of energy shells in the atom

17. Group / Family – the vertical columns on the Periodic Table
Group / Family – the vertical columns on the Periodic Table. Families share similar chemical properties.

18. The Group Number Rule – Elements in a group have the same number of valence electrons
Notice Helium is the only exception, but belongs with the noble gases (full valence shell)

19. Notice Hydrogen is not an Alkali Metal
Alkali Metals – highly reactive metals that react intensely with water and air. All Alkali Metals have 1 valence electron
Alkali Metals are NEVER found in nature; they are TOO REACTIVE
Notice Hydrogen is not an Alkali Metal
Group Number : 1
Valence Electrons: 1

20. Alkaline Earth Metals – reactive metals that react slowly with water and air. All alkaline earth metals have 2 valence electrons
Not found in nature in pure form (too reactive)
Group Number : 2
Valence Electrons: 2

21. Valence Electrons: varies
Transition Metals – these metals are generally more stable and less reactive. The most stable elements are in the middle of the table.
Group Number :
Valence Electrons: varies

22. Halogens – extremely reactive nonmetals, with 7 valence electrons
Halogens – extremely reactive nonmetals, with 7 valence electrons. Halogens react with hydrogen gas and most metals to form stable compounds.
Group Number : 17
Valence Electrons: 7

23. Except Helium (2 valence electrons)
Noble Gases – nonreactive, stable gases. Every Noble Gas has a full valence shell.
Group Number : 18
Valence Electrons: 8
Except Helium
(2 valence electrons)

24. Malleable (they can bend and be shaped)
Properties of Metals
Silvery and shiny
Malleable (they can bend and be shaped)
Good conductors of heat and electricity
Magnesium
Nickel

25. Properties of Metalloids
Share properties of both metals and nonmetals
Semi-conductor of electricity

26. Properties of Nonmetals
Solids, liquids, and gases (most are gases)
Solids are brittle
Poor conductors of heat and electricity

27. Honors section