Terms in this set (43)
-Particles are too small to be seen
-Particles are called atoms
-Atoms mostly empty space
DALTON thought that atoms were?
-Solids, round particles of matter (incorrect thinking)
-Different elements have different atoms
-Combine to make compounds
-Called Billiard Ball Model (pool balls)
-"Plum Pudding " model
-Negative particles mixed equally in a positive material
-Used cathode ray tube to discover electron
-(e-) - has very little mass
-Discovered alpha particle (a)
-Did gold foil experiment
-Discovered nucleus with positive particles called protons -(p+) - 7000x heavier than electron
-Atom mostly empty space
-electrons outside the nucleus
-Overall charge on atom is neutral
-While working with Bohr discovered the neutron
-Said neutron has no charge and is in the nucleus
-Neutron has no charge (neutral)
-Mass is about equal to proton
-Nucleus has protons and neutrons (n0)
-Planetary model ; Electrons have fixed paths (orbits or energy levels) around nucleus
(electrons do not have fixed paths in real life.)
-Each can hold only so many electrons
1st orbit (energy level) holds 2 e-
2nd holds 8
3rd holds 18 e
-Called electron cloud model
-Shows area in space where different electrons are most likely to be found according to their energy levels
-Electrons are moving so fast you can't pinpoint their exact location
-energy levels are areas where electrons are most likely found
where are atoms?
atoms are everywhere!
what is an atom?
-The smallest unit of a substance that behaves like the substance
-The building block of all matter
-Is responsible for the properties of a substance
Parts of an atom?
nucleus, protons, neutrons, electron cloud, and electrons
Dense heavy center of atom that contains protons and neutrons ; overall positive charge
(+) - Massive positively charged particle; found in the nucleus; identifies element
(N) - Massive neutral (no charge) particle; found in the nucleus
Large area surrounding the nucleus made of electrons and mostly empty space.
(-) - "Swarms" around the nucleus in a cloud;
negatively charged particle with very little mass; the charge usually balances out the charge of the protons.
how many different kinds of atoms/ elements do we know of ?
at least 115
There are different numbers of particles in each element thereby giving each different properties.
How do we know how many of each particle each different element has?
Finding Protons and Electrons
atomic number (Z) -
Tells number of protons and electrons (in a neutral atom) -Identifies element
-Puts periodic table in order
-Placed in lower left hand corner of symbol.
-mass number (A) - Tells the number of neutrons plus protons.
-Atomic mass (He - 4.002602) rounded off to nearest whole number
-MASS # - ATOMIC # = Number of neutrons
-Placed in upper left hand corner of symbol
ATOMS, ISOTOPES, AND IONS
Changing of Protons results ?
a new element
Changing of Neutrons results in?
An isotope :
A HEAVIER (OR LIGHTER) FORM OF THE SAME ELEMENT
Changing of Electrons results in?
A charged (positive or negative) form of the same element called an ion
Is found on the periodic table
Has an overall charge of zero
-Has a different number of neutrons than what is found on the periodic table
-Has a different atomic mass than what is found on the periodic table
-Is written with an isotopic symbol
Example: H - 3
same or different element?
Determined by # of protons (Atomic #)
- An ion created from a metal with a overall positive charge
- An ion created from a nonmetal with an overall negative charge
Purpose of ions:
Stability AND Chemical Bonding
their respective charges are
positive, neutral, and negative
the 3 particles of the atom are
proton, neutron, electron
in 1860 how many elements were known?
what group of elements had not been discovered yet?
why aren't the period patterns not consistent?
some were not discovered they were missing
what groups should be apart of the main periodic table? why were they pulled out?
lanthanides and actinides, they all wouldn't fit on the paper
what do the letters represent on the table ?
they come from their orgin
what does the atomic number tell you?
protons and electrons
why do elements like sodium and gold not have symbols that reflect their name?
came from latin words
how many elements are on the periodic table ?
how many elements are found in nature? if not found in nature where are they found?
94 and factories
most common element in the human body?
what is found in the cloud of an atom?
the organization of the periodic table helps us ?
helps us predict how two elements combined
the number of electrons determines the ?
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