unit 1 Flashcards
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
what is electronegativity
-number that describes availability of an atom when bonded to an electron
what is the trend in electronegativity
decreases going down a group and increases across a period
what is compound formation
-when valence electrons make a new arrangement that has less energy than their previous arrangement
how do you show an ionic bond
using louis dot diagrams
what is a formula unit
simplest whole number ratio of atoms and ions of an element in an ionic compound
ex. NaCl has 1:1 ratio
what is a crystal lattice
a regular ordered arrangement of atoms, ions, or molecules
what are the three types of covalent bonds
-single (one pair of electrons share)
-double (two pairs of electrons shared)
-triple (three pairs of electrons shared)
what is a lone pair
electrons not involved in bonding
what is electrical conductivity
-the ability of material to allow electricity to flow through it
-solutions that conduct electricity are called electrolytes
what are the rules for drawing structural diagrams
-central element - element with highest bonding capacity or lowest electronegativity
-arrange elements
-count total # of valence electrons
-place a pair of electrons between each element
-place lone pairs around surrounding elements (not central)
-if more electrons left over put them around central
-make sure all elements are happy, if not use co-ordinate covalent
what is a polyatomic ion
-it is an ion with a charge
-positive = less electrons, negative = more electrons
how do you draw a structural diagram for a polyatomic ion
-do all same steps as before
-when counting valence electrons add one for each unit of negative charge or subtract one for each unit of positive charge
-draw brackets around structure with its charge outside
what are the three types of bonds
-ionic
-polar
-non-polar
what is the electronegative of an ionic compound
-1.7 or more
what are polar covalent bonds
-when electrons are not shared equally
-difference between 0.39 and 1.69
-on is partially positive and the other is partially negative (the higher electronegativity is negative)
-draw arrow to show which element is the hog
what is a non-polar covalent bond
-electrons shared equally
-difference between 0 and 0.39
-shared equally so no charge or arrow
what is nuclear charge
charge in nucleus, more protons = strong which pulls in electrons and creates smaller radius
