Eleven are gases at room temperature, six are ________, and one is a liquid.
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Chemical reactions
________ change only the way that atoms are combined in compounds.
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Russian chemist
In 1869, the ________ Dmitri Mendeleev organized the elements in order of increasing mass and then organized elements into groups based on similarities in chemical behaviour.
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neutrons
The protons and ________ are packed closely together in a dense core called the nucleus.
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spin
Each orbital can hold only two electrons, which differ in a property known as ________.
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Z
Each atom has a specific number of protons, neutrons, and electrons, and the identity of the element is determined by the number of protons within the nucleus, also called the elements atomic number (________)
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→The metalloids
________ are located in a zigzag band between the metals on the left and non- metals on the right side of the periodic table.
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→18 elements
________ are non- metals.
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Bromine
________ is the only liquid non- metal.
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→Group 7A Halogens
________: Fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At) are colourful and corrosive non- metals.
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metals aluminum
→ 94 are classified as ________, gold, copper, and zinc, for example.
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periodic table
The ________ can be divided into four regions, or blocks, of elements according to the electron shells and subshells occupied by the subshell filled last.
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valence electrons
Because the ________ are the most loosely held, they are the most important in determining an elements properties.
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Atoms
________ are composed of tiny subatomic particles called protons, neutrons, and electrons.
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→RULE
________ 2: Each orbital can hold only two electrons, which must be of opposite spin.
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Group 1A-Alkali metals
Lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr) are shiny, soft metals with low melting points
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Group 2A-Alkaline earth metals
Beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra) are also lustrous, silvery metals but are less reactive than their neighbours in group 1A
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Group 7A-Halogens
Fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At) are colourful and corrosive non-metals
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Group 8A-Noble gases
Helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn) are colourless gases
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Within shells, electrons are further grouped into subshells of four different types, identified in order of increasing energy by the letters s, p, d, and f. The first shell has only one subshell, s. The second shell has two subshells
an s subshell and a p subshell
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→RULE 1
Electrons occupy the lowest-energy orbitals available, beginning with 1s
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→RULE 2
Each orbital can hold only two electrons, which must be of opposite spin
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→RULE 3
Two or more orbitals with the same energy are each half-filled by one electron before any one orbital is completely filled by the addition of the second electron
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three isotopes of hydrogen
protium, deuterium, tritium.
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atomic mass number (A)
The sum of the protons and neutrons
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isotopes
Atoms with identical atomic numbers but different atomic mass
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