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Atom
what is atom?
Dalton’s atomic theory of matter:
Pure (24K) gold is composed of only one type of atom which is gold atoms.
Every element has at least one isotope, and many elements have multiple isotopes.
atom
An atom is the smallest unit of matter that retains all of the chemical properties of an element.
In 1661, Robert Boyle first published the theory that all matter was composed of atoms.
Brown, LeMay, Busten, Murphy, Woordward. Atoms, molecules and ions (summary) [internet].. UC Davis and California State University. 2019 Jun 6 [cited 2019 Sep 1]. Available from: https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Chemistry_-_The_Central_Science_(Brown_et_al.)/02._Atoms%2C_Molecules%2C_and_Ions/2.S%3A_Atoms%2C_Molecules%2C_and_Ions_(Summary)
All atoms of a given element are identical; the atoms of different elements are different and have different properties
Atoms of an element are not changed into different types of atoms by chemical reactions
chemical reactions
Compounds are formed when atoms of more than one element combine
modern view of atomic sturture
charge of an electron is –1.602*10-19
charge of a proton is +1.602*10-19
1.602*10-19 is called to electronic charge
homonuclear
what is molecules
molecules
two or more atoms bonded together
heteronuclear
what is ion
ion
an atom or molecule that has gained or lost one or more of its valence electrons, giving it a net positive or negative electrical charge.
+
positive ion
Cations are ions that carry a net positive charge because the number of protons in the species is greater than the number of electrons.
_
Negative Aspects
Anions are ions that carry a net negative charge. In anions, there are more electrons than protons.
Mendeleev
atom according to Mendeleev's system
explanation
Mendeleev periodic table initialy only have 63 element
elements with similar properties fell into vertical columns in his table.
element are arranged in the increasing relative mass oreder
1. Dmitri Mendeleev [Internet]. Khan Academy. 2019 [cited 2 October 2019]. Available from: https://www.khanacademy.org/partner-content/big-history-project/stars-and-elements/knowing-stars-elements/a/dmitri-mendeleev
Mendeleev divided his periodic table into eight groups and seven period
groups one to seven are meant for normal atom while the eight is for transition element
contain of:
-alkaline metals
-alkaline earth metals
-halogens
-noble gases
modern periodic table
Brown, LeMay, Busten, Murphy, Woordward. The periodic table. [internet]. UC Davis and California State University. 2019 Sep 9 [cited 2019 Sep 30]. Available from: https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Chemistry_-_The_Central_Science_(Brown_et_al.)
molarity,
the concentration of a solution expressed as the number of moles of solute per liter of solution
molarity
molality,
molality is a property of a solution defined as the number of moles of solute per kilogram of solvent
molality
normality
Normality is a measure of concentration equal to the gram equivalent weight per liter of solution.