unit 1 Flashcards
(41 cards)
what is an isotope
-atoms of an element that have same number of protons (atomic number) but different number of neutrons (atomic mass)
how is an isotope written
carbon - 14
or
35 —> atomic mass
Cl
17 —> atomic number
what is isotopic abundance
-the percentage of a given isotope in a sample of an element
-percents of isotopes of same element add to 100%
what is a radioisotope
-isotopes which can decay and emit radiation as their nucleus changes
what is the formula for finding the atomic mass of an isotope
atomic mass =
% abundance of isotope 1(mass of isotope 1)
+
% abundance of isotope 2(mass of isotope 2)
what are the trends in a group in the periodic table
-have same chemical properties and reactivity bc same number of valence electrons
-for metals reactivity increases moving down a group
-for non-metals reactivity decreases moving down a group
what are the rules to follow for atoms containing many electrons
1) electrons always occupy the lowest possible energy level (orbital)
2) there is a maximum number of electrons in each level
—> the number is given by 2n^2 where n is the principle quantum number
what was Mendeleev’s periodic table
-chemists who published the first periodic law
-elements arrange in order of increasing atomic mass show a periodic recurrence of properties
how is the modern periodic table organized
-after Mendeleev the periodic law was revised
-when elements are strange in order of increasing atomic numbers their properties show a periodic recurrence and gradual change
what is atomic radius
-a measurement of the size of an atom
-atomic radii decrease from left to right across a period
what is nuclear charge
-charge in nucleus
-more protons in nucleus = stronger charge that pulls electrons in and creates smaller radius
What are IONIC properties?
-high melting point
-conduct electricity when liquid or in solution
What are the MOLECULAR properties?
-low melting points
-do not conduct
-atoms shared equally —> molecule non-polar
-atoms not shared —>molecular polar
What did The Alchemist do?
-made lab glassware, equipment, procedures, and processes that are still used today
What was Daltons theory?
-all matter is made up of tiny invisible particles called atoms
-all atoms of an element are identical
-atoms of different elements are different
-atoms are rearranged to form new substances in chemical reactions but cannot be created or destroyed
What did Thomson discover?
-discovered the electron
-proposed that they are negatively charged small part of an atom
-made plum pudding model
What did Rutherford do?
-aimed alpha particles at a sheet of gold foil and measured how much the foil deflected particles
-guessed that they would go through
-was proven wrong because some deflected (they hit protons)
-concluded that atoms have a small, dense, positively charged, central nucleus
What did Chadwick discover
nuclei contain neutral particles known as neutrons
What did Bohr discover?
-electrons are in orbits of differing energy (energy levels)
-electrons start at ground level but can absorb energy and go to excited state
-after being excited they release energy and this energy occupies a portion of the electromagnetic spectrum
-different energy levels have different numbers of electrons
-the bohr model only works for simple atoms
what is ionic radius
-measure of the size of an atom
-metal ions get smaller because they lose electrons
-non metals get larger bc they gain electrons
what is ionization energy
-amount of energy required to move an electron from an atom
-energy varies depending on which electron is being bc removed (closer to nucleus = more energy needed to remove)
what is first ionization energy
-amount of energy required to remove most weakly held electron
what is the trend in ionization energy
-increases going up a group
-increases across a period
—> metals want to give away electrons to be stable so it requires less energy
what is electron affinity
energy charge that occurs when an electron is accepted by an atom
