Date post: | 11-Jan-2016 |
Category: |
Documents |
Upload: | brooke-burke |
View: | 223 times |
Download: | 0 times |
Chapter 15 – Elements & The Periodic Table
15.1 The Periodic Table of the Elements– (pp. 334-340)
Periodic Table Timeline
Lavoisier (1770-1789) Composed the first list of 33 elements. Distinguished metals from nonmetals.
Berzelius (1828) Created a table of atomic weights. Introduced idea of chemical symbols.
Dobereiner (1829) Developed triads-groups of 3 elements with similar properties.
Newlands (1864) Arranged known elements in order of increasing atomic weights. Proposed the Law of Octaves.
Meyer (1869) Compiled a periodic table with elements arranged by atomic weight. Elements with similar properties arranged in columns.
Mendeleev (1869) Created a periodic with elements arranged by atomic weight. Elements with similar properties arranged in columns.
Ramsay (1894) Discovered noble gases.
Moseley (1914) Determined atomic numbers of each element. Modified the periodic law-an element’s properties varies periodically with its atomic numbers.
Seaborg (1940) Synthesized elements beyond uranium.
15.1 Physical properties
Characteristics that you can see through direct observation are called physical properties.
Physical properties include color, texture, density, brittleness, and state (solid, liquid, or gas).
Melting point, boiling point, and specific heat are also physical properties.
15.1 Physical properties
A physical change does not result in a new substance being formed.
15.1 Chemical propertiesProperties that can only be observed
when one substance changes into a different substance are called 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
The periodic table is further divided into periods and groups.
Each horizontal row is called a period.
Each vertical column is called a group or family.
15.1 Atomic Number Remember, the atomic number is the number of
protons all atoms of that element have in their nuclei. This number does not change for that element.
If the atom is neutral, it will have the same number of electrons as protons.
15.1 Atomic Mass The mass of individual atoms is so small
that the numbers are difficult to work with. To make calculations easier, scientists use
the atomic mass unit (amu). The atomic mass of any element is the
average mass (in amu) of an atom of each element.
15.1 Atomic Mass Atomic masses differ
from mass numbers because most elements in nature contain more than one isotope.
15.1 The Periodic Table All the elements in Group
1 of the periodic table form similar compounds.
The metals lithium, sodium, and potassium all form compounds with a ratio of 2 atoms of the metal to 1 atom of oxygen.
GROUPS 1 & 2VERY REACTIVE METALSGroup 1 – The Alkali Metals
The most reactive metals1 electron in outer energy levelOther shared properties – soft, silver colored; shiny; low
density
Group 2 – The Alkaline Earth Metals-very reactive, but less reactive than alkali metals
2 electrons in outer energy levelOther shared properties – silver colored; more dense than
alkali metals
THE TRANSITION METALS
Groups 3-12 1 or 2 electrons in outer energy level Less reactive than alkaline earth metals Lanthanides and actinides are included in this
group Other shared properties: shiny; good
conductors of thermal energy and electric current; higher densities and melting points than elements in Groups 1 & 2
LANTHANIDES
They follow the element Lanthanum.
Shiny, reactive metals
ACTINIDES
They follow the element Actinium All are radioactive. This means they are
unstable. Elements listed after Plutonium (element
94) do not occur in nature. They are man made.
GROUP 13
Also known as the Boron Group 3 electrons in the outer energy level Group contains Boron (a metalloid) and 4 metals
(Al - aluminum, Ga - gallium, In - indium & Tl- thallium)
Reactive Other shared properties: solid at room
temperature
GROUP 14
Also known as the Carbon Group 4 electrons in outer energy level Reactivity varies among the elements Group contains 1 nonmetal (carbon), 2
metalloids (Si - silicon & Ge - Germanium) and 3 metals (Sn - tin, Pb - lead and Uuq)
Other shared properties: solid at room temperature
GROUP 15
Also known as the Nitrogen Group Have 5 electrons in the outer energy level Reactivity varies among the elements Group contains 2 nonmetals (N - nitrogen & P -
phosphorus), 2 metalloids (As- Arsenic & Sb - antimony) & 1 metal (Bi - bismuth)
Other shared properties: all but Nitrogen are solid at room temperature
GROUP 16
Also known as the Oxygen Group Have 6 electrons in the outer energy level Very reactive Contains 3 nonmetals (O - oxygen, S - sulfur &
Se - selenium), 1 metalloid (Te - tellurium) & 2 metals (Po - polonium & Uuh)
Other shared properties: all but Oxygen are solid at room temperature
GROUP 17
Also known as the Halogens Group contains all nonmetals (F - fluorine, Cl -
chlorine, Br - bromine, I – iodine & At - astatine) Very reactive There are 7 electrons in the outer energy level Other shared properties: poor conductors of
electric current; react violently with alkali metals to form salts; never found uncombined in nature.
GROUP 18
Also known as the Noble Gases Group contains all nonmetals (He - helium, Ne -
neon, Ar - argon, Kr - krypton, Xe - xenon, Rn – radon & Uuo)
There are 8 electrons in the outer energy level (He only has 2)
They are unreactive. Other shared properties: colorless, odorless
gases at room temperature
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.