Unit 1: Atoms and the Periodic Table Overview
Click on each individual unit standard to see an in-depth view of what we are learning in 8th grade science:
(8.5A) Structure of Atoms
(8.5A) Students will describe the structure of atoms, including the masses, electrical charges, and locations, of protons and neutrons in the nucleus and electrons in the electron cloud.
- Atom – smallest particle of an element that maintains the properties of that element
Properties of an atom - Mass number – total number of protons and neutrons in a specific atom
- Atomic number – the number of protons in the nucleus of an atom; used to
determine that element's position in the Periodic Table - Mass / size comparison
- Protons and neutrons have a similar mass and size (1 amu)
- Electrons are significantly smaller in mass and size than protons and neutrons
- Electrical charge
- Subatomic particle – a particle smaller than an atom, such as a proton, neutron, or
electron- Electron – a negatively charged particle in the electron cloud surrounding the
atomic nucleus - Proton – positively charged particle within the atomic nucleus
- Neutron – a (neutral) particle with no electrical charge within the atomic
nucleus
- Electron – a negatively charged particle in the electron cloud surrounding the
- Nucleus – the positively charged center of an atom containing the protons and
neutrons - The nucleus is positively charged because the only electrically charged particles
present are protons
- Subatomic particle – a particle smaller than an atom, such as a proton, neutron, or
- Locations
- Nucleus (protons and neutrons) - Makes up the mass of the atom
- Electron cloud – the negatively charged space, containing electrons, that surrounds
the atomic nucleus- The electron cloud makes up the majority of the volume of the atom (mostly empty space)
- Valence electron(s) – electron(s) located in outer energy level (electron shell)
- Relationship of atomic structure to Periodic Table
- Periodic Table – a conceptual model in which the elements are organized according
to their properties; often displayed as a chart - Atomic number (location on Periodic Table) - Number of protons in nucleus
- Mass number (given or calculated)
- Protons plus neutrons in nucleus
- Calculate number of neutrons by subtracting the atomic number from the
mass number
- Calculate total number of protons, neutrons, and electrons in an atom of an element
- APE MAN Method - Atomic Number = # of Protons = # of Electrons ; Mass - Atomic # = # of Neutrons
- Periodic Table – a conceptual model in which the elements are organized according
(8.5B) Protons and Valence Electrons
(8.5B) Students will identify that protons determine an element's identity and valence electrons determine its chemical properties, including reactivity.
- Protons
- Determine an element’s identity (atomic number)
- Number of protons will be less than or equal to number of neutrons
- Determine an element’s identity (atomic number)
- Valence electrons
- Determine an element’s chemical properties
- Reactivity resulting from incomplete outer electron energy level (electron shell)
- Determine an element’s chemical properties
(8.5C) Interpreting the Periodic Table
(8.5C) Students will interpret the arrangement of the Periodic Table, including groups and periods, to explain how properties are used to classify elements.
- Periods
- The horizontal rows on the Periodic Table are periods
- Patterns
- Atomic number and mass increase from left to right across a period
- Energy levels increase from top to bottom (e.g., Period 2 has 2 energy levels, Period 5 has 5 energy levels)
- Groups (families)
- The vertical columns on the Periodic Table are groups or families with similar properties
- Chemical properties
- Reactivity
- Valence electrons
- Group 2 has 2 valence electrons
- Group 18 has a full outer (valence) energy level (electron shell)
- Physical properties
- State of matter
- Metals, nonmetals, metalloids
- Conductors, insulators
- Placement of elements on the Periodic Table
- Atomic number
- Atomic mass
- Reactivity (valence electrons)
- Groups 1 and 2 (most reactive metals)
- Group 18 (noble gases – non-reactive, stable, full outer energy levels
(electron shells))