Chemistry Stage 2

Dmitri Mendeleev

classified the elements then discovered in increasing order of atomic weight,

How many elements exist?

118

how many elements are found in nature?

94

International Union of Pure and Applied Chemistry (IUPAC)

network of scientists organized into eight specialties from chemistry societies around the world. 

Compiled by Aristotle and Plato

one of the first attempts to group the elements was a table that only included 20 elements

Metallurgy

The science and technology that studies metals, their extraction from minerals, and their transformation to obtain useful materials. 

copper

the first metal to be worked

when combined they formed new substances.

metal alloys

John newlands and chancourtois

proposed the law of octaves

Physical properties of elements

Atomic number, atomic mass, electronegativity, density, melting point, boiling point, van der waals radius, ionic radius

Physical properties of metals

luster, hardness, malleability, ductility, conductivity

Physical properties of nonmetals

They don´t corrode

They are britthe and opaque 

They can be liquid, solid or gas 

lower melting and boiling points than metals 

they don´t reflect light and may have varied colors. 

they are found in the Earth´s crust and in the atomosphere. 

They have four or more electrons in their valence shells. 

periodic trends

patterns in the properties of chemical elements that repeat in a predictable way across the Periodic Table as atomic number increases, properties that increases or decreases across a period

metallic character

element that loses valence eletrons easily, more prevalent in the elements on the left side of the periodic table (metals) and decreases going from left to right across a period,

atomic radius (atomic size)

Determined by the distance of the valence electrons from the nucleus. For each group of reprresentative elements, the atomic size increases going from the top to the bottom

Ionization energy

Energy required to remove an electron from an atom. Increases going from left to right across the periodic table

Electronegativity

Ability of an atom to attract electrons, increases from left to right along the periods

Difference between 0 and .4

nonpolar covalent bond

Difference greater than .5 and less than 1.6

polar covalent bond

greater than 1.7

ionic bond

chemical bonds

chemical processes generated by attractive interactions between atoms and molecules that provide stability to chemical compounds, the force that holds two atoms together in a compound and makes them to work as a unit

Bonding energy

force required to break the chemical bond.

inonic bond

metal + nonmmetal

covalent bond

between nonmetalic