15.1 The Periodic Table of the Elements

Periodic Table Timeline Lavoiser (1770-1789) Composed the first list of 33 elements. Distinguished metals from nonmetals.

Meyer (1869) Compiled a periodic table with elements arranged by atomic weight. Elements with similar properties arranged in columns. Mendeleev (1869) Created a periodic table with elements arranged by atomic weight. Elements with similar properties arranged in columns. Moseley (1914) Determined atomic numbers of each element.

15.1 Physical properties Remember phase changes are physical changes.

15.1 Chemical properties Any change that transforms one substance into a different substance is called a chemical change.

15.1 The Periodic Table The periodic table organizes the elements according to how they combine with other elements (chemical properties). The periodic table is organized in order of increasing atomic number.

15.1 The Periodic Table Each horizontal row is called a period. Each vertical column is called a group or family.

Elements Metals Nonmetals Metalloids

Metals Almost 75% of elements are metals Most are solids at room temperature exception-Hg(mercury)

Alkali Metals(Group 1) Very reactive Shiny and light weight Only found combined with other elements One electron in their outer shell

Alkaline Earth Metals (Group 2) Not as reactive as the alkali metals Have 2 electrons in the outer shell

Transition Metals (Groups 3 to 12) Less reactive than alkali or alkaline earth metals Properties vary widely examples: Hg –liquid, titanium is not very reactive but iron is. Electrons in the 2 outer most shells can bond with other elements

Groups 13 to 16 Boron Group III - 3 electrons in the outer shell Carbon Group IV-4 electrons in the outer shell Nitrogen Group V - 5 electrons in the outer shell Oxygen Group VI -6 electrons in the outer shell

Halogens VII(Group 17) Very reactive nonmetal Seven electrons in the outer shell Often bond with metals Fluorine is the most reactive Never found uncombined in nature Form halides-a halogen combined with another element to form a compound

Noble Gases VIII (Group 18) Have full outer shell with 8 electrons, except for Helium which has 2. Rarely combine with other elements Non-reactive (inert) Colorless and Odorless Gases at room temperature

Groups with Metalloids Groups 13 to 16 shift from metals to nonmetals with some metalloids in between They have properties of both metals and nonmetals

Lanthanides/Inner Transition Metals Follow the element lanthanum Shiny and reactive Used to make different types of steel

Actinides Follow the metal actinium Radioactive Unstable

Carbon and carbon-like elements Almost all the molecules that make up plants and animals are constructed around carbon. The chemistry of carbon is so important it has its own name, organic chemistry.

Nitrogen, oxygen and phosphorus Oxygen and nitrogen are crucial to living animals and plants. For example, proteins and DNA both contain nitrogen. Phosphorus is a key ingredient of DNA, the molecule responsible for carrying the genetic code in all living creatures.

15.2 Nitrogen, oxygen and phosphorus Phosphorus is a key ingredient of DNA, the molecule responsible for carrying the genetic code in all living creatures. When phosphorus atoms absorb light, they store energy, then release it in a greenish glow.

HYDROGEN Stands apart Only 1 electron in the outer energy level Very reactive Other properties: colorless, odorless gas at room temperature; low density; reacts explosively with oxygen.

15.2 Periodic properties of elements Periodicity means properties repeat each period (row) of the periodic table.

Energy Levels And The Periodic Table The periods (rows) of the Periodic Table correspond to the energy levels in the Bohr model of the atom. The first energy level can accept up to two electrons therefore Period 1 is the first energy level. Period 2 is the 2nd energy level Period 3 is the third energy level and so on.

Energy Levels And The Periodic Table The outermost electrons in an atom are the ones that interact with other atoms. They are also the electrons that are in the highest energy level. Electrons in the completely filled inner energy levels do not participate in forming chemical bonds.