Presentation on theme: "Atomic Structure and the Periodic Table Chapter 2-1."— Presentation transcript:
Atomic Structure and the Periodic Table Chapter 2-1
Chemical symbols Abbreviated way to write the name of an element Always starts with a capital letter If double letters – first is capitalized second is lower case Cl Ar Ne
atom Smallest part of matter Basic building block of matter Parts of an atom – Nucleus – center – – protons - + charge – neutrons - neutral charge size: mass p = mass n
Electron cloud – Surrounds the nucleus – Contains electrons – Electrons have a negative charge – Size: mass e = 1/2000 of m p – mass so tiny that it isn’t even considered in the mass of an atom – Moves around the nucleus at such speeds that they cannot be seen. – Cloud like appearance
– Neutral atom – the number of positive charges equal the number of negative charges – All elements on periodic table are stable atoms.
Atomic number Number of protons in an atom Every atom of the same element has the same atomic number Identity number of an element
Danish scientist Neils Bohr 1913 Developed the first model of what the atom looks like
Bohr diagram Central nucleus Electrons moving around it in well defined paths or orbits.
Electron clouds Electrons moving so fast that they cannot be seen Electrons move within a certain region NOT on orbits
Energy Levels and Electrons Electrons are at varying distances from nucleus – e near nucleus – low energy – e farther from nucleus – high energy
Energy levels – Each holds a different amount of electrons – There is a maximum number of electrons each can hold