Chapter 4 - Atomic Theory, Atoms, Elements and Ion Notes Flashcards
Dalton’s Atomic Theory
year 1808
- Elements are made of tiny particles called atoms.
- All atoms of a given element are identical.
- The atoms of a given element are different from those of any other element.
- Atoms of one element can combine with atoms of other elements to form compounds.
- Atoms are not created or destroyed in chemical reactions. A chemical reaction simply changes the way the atoms are grouped together.
JJ Thomsom
1897 discovered electrons in Cathode Ray experiments.
E. Goldstein
1900 discovered protons in Anode Ray experiment
E. Rutherford
1911 discovered the nucleus and provide the basis for the modern atomic structure through his alpha particle scattering experiment.
James Chadwick
1932 discovered neutrons
N. Bohr
1940 provided the modern concept of the atomic model.
Proton
positively charged particle found inside the nucleus
Neutron
uncharged particle found inside the nucleus
electron
negatively charged particle found orbiting outside of the nucleus.
atomic number
number of protons
atomic mass
number of protons plus the number of neutrons
number of protons and electrons in a neutral atom are
equal.
isotopes
atoms with the same number of protons but with a different number of neutrons. the atomic number stays the same. The atomic mass is different.
ions
occur when electrons have been added or removed from a neutral atom.
cation
an ion with a positive charge. electrons have been removed
anion
an ion with a negative charge. electrons have been added.
diatomic elecments
these are molecules made up of 2 atoms of the same element.
diatomic elements found on the periodic tables are:
hydrogen (h2), oxygen (O2), nitrogen (n2), fluroine (F2), chlorine (CL2), bromine (Br2) and iodine (I2).
Periodic Table
- vertical columns are known as groups
- horizontal rows are known as periods
- elements are organized by increasing atomic number
- elements are categorized as metals, nonmetals or metalloids.
- elements can be solids, liquids or gases at 25 C .
Groups
these elements are grouped together based on similar chemical properties
group 1
alkali metals
group 2
alkaline earth metals
group 3
12 transitional metals
group 17 or 7
halogens
groups 18 or 8
noble gases
Element States at room temperature
the majority of elements are solid at room temp (25C)
except:
mercury (Hg) and bromine (br2) are the only two elements that are liquids at 25 C
and
Gases at 25 C are: hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon and radon.
metals
- conduct heat and electricity
- malleable - can be hammered into thin sheets
- ductile - can be pulled into wires.
- shiny appearance (luster)
- most are solids at 25 C (room temp)
nonmetals
- brittle
- usually lack the properties of metals
- most do not conduct heat or electricity
- most are no malleable
- most are no ductile
- most do not have a shiny appearance (lack luster)
mettaloids
- have a mixture of metallic and nonmetal properties
Si - silicon, As-arsenic, Te-tellurium, Ge- germanium, and Sb- antimony
compounds
a compound is composed of 2 or more elements from the periodic table.
chemical formulas for compounds
are written with the element symbols and a subscript to indicate the number of each type of atom present.
H2O
