Ch. 16 Properties of Atoms & the Periodic Table

Structure of the Atom Structure of the Atom Element: Element: matter made of one type of atom matter made of one type of atom Abbreviated with a scientific symbol, usually the first letter or two of the elements name Abbreviated with a scientific symbol, usually the first letter or two of the elements name Ex: H=hydrogen, C=carbon, He=helium Ex: H=hydrogen, C=carbon, He=helium

Structure of the Atom Structure of the Atom Element: Element: Atom: smallest part of matter that still has the properties of the element Atom: smallest part of matter that still has the properties of the element 3 parts of an atom: 3 parts of an atom: Proton: has a positive electrical charge Proton: has a positive electrical charge Neutron: has a neutral charge Neutron: has a neutral charge Electron: has a negative charge Electron: has a negative charge Protons and neutrons are found in the nucleus of an atom Protons and neutrons are found in the nucleus of an atom Electrons surround the nucleus Electrons surround the nucleus

Structure of the Atom Structure of the Atom Protons & neutrons are made up of smaller particles called quarks. Protons & neutrons are made up of smaller particles called quarks. Quarks are studied by colliding accelerated charged particles with protons, which leave tracks in a bubble chamber. Quarks are studied by colliding accelerated charged particles with protons, which leave tracks in a bubble chamber. Six quarks are known to exist Six quarks are known to exist The 6 th quark is known as the top quark The 6 th quark is known as the top quark

Structure of the Atom Structure of the Atom Scientists use scaled-up models to represent atoms. Scientists use scaled-up models to represent atoms. Early models used a solid sphere. Early models used a solid sphere. The current electron cloud model shows electrons traveling in specific energy levels around a nucleus of protons and neutrons. The current electron cloud model shows electrons traveling in specific energy levels around a nucleus of protons and neutrons.

Masses of Atoms Masses of Atoms Atomic mass: composed mostly of the protons and neutrons in the nucleus Unit of measurement for atomic particles is atomic mass unit (amu) which is one-twelfth the mass of a carbon atom containing six protons and six neutrons.

Masses of Atoms Masses of Atoms Atomic number: the number of protons in an atom; number of protons also identifies the element The sum of the number of protons and neutrons in the nucleus of an atom is the mass number.

Masses of Atoms Masses of Atoms Isotopes—atoms of the same element with different numbers of neutrons Different isotopes have different properties. Number of neutrons is equal to mass number minus atomic number. Name of element followed by mass number identifies the isotope. Average atomic mass is the weighted- average mass of an element’s isotopes. Average atomic mass is closest to its most abundant isotope.

The Periodic Table The Periodic Table Elements are organized in the periodic table by increasing atomic number. In the late 1800’s, Dmitri Mendeleev devised the first periodic table based on atomic mass. In 1913, Henry G. J. Moseley arranged the elements by atomic number rather than atomic mass.

The Periodic Table The Periodic Table Vertical columns in the periodic table are groups of elements with similar properties. Elements in the same group have the same number of electrons in their outer energy level.

The Periodic Table The Periodic Table Each of the seven energy levels can have a maximum number of electrons. Energy level one can contain at most two electrons. Energy level two can contain at most eight electrons.

The Periodic Table The Periodic Table Each row in the periodic table ends when an outer energy level is filled. Electron dot diagrams use the element symbol and dots to represent outer energy level electrons.

The Periodic Table The Periodic Table Periods—horizontal rows of elements that contain increasing numbers of protons and electrons. Elements are classified as metals, nonmetals, or metalloids (semimetals). Elements are synthesized in laboratories all over the world.

The Periodic Table The Periodic Table The same elements exist all over the universe. Hydrogen and helium are the building blocks of other naturally occurring elements. Supernovas spread heavier elements throughout the universe.