Chapter 4
Idea of an Element
A chemical element is a substance that cannot be broken down by chemical means. Elements are defined by the number of protons they possess.
A chemical element is a substance that cannot be broken down by chemical means. Elements are defined by the number of protons they possess.
Dalton's atomic theory:
Dalton's theory was based on the premise that the atoms of different elements could be distinguished by differences in their weights.
The theory proposed a number of basic ideas:
All matter is composed of atoms
Atoms cannot be made or destroyed
All atoms of the same element are identical
Different elements have different types of atoms
Chemical reactions occur when atoms are rearranged
Compounds are formed from atoms of the constituent elements.
Compounds and Chemical Formula
In simple terms compounds can be described as substances that have two or more Atoms bonded together. Definition of a compound. A compound is a pure substance that contains atoms of two or more chemical elements in definite proportions that cannot be separated by physical means and are held together by chemical bonds.
A chemical formula is a way of expressing information about the proportions of atoms that constitute a particularchemical compound, using a single line of chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, and plus (+) and minus (−) signs.
Dalton's theory was based on the premise that the atoms of different elements could be distinguished by differences in their weights.
The theory proposed a number of basic ideas:
All matter is composed of atoms
Atoms cannot be made or destroyed
All atoms of the same element are identical
Different elements have different types of atoms
Chemical reactions occur when atoms are rearranged
Compounds are formed from atoms of the constituent elements.
Compounds and Chemical Formula
In simple terms compounds can be described as substances that have two or more Atoms bonded together. Definition of a compound. A compound is a pure substance that contains atoms of two or more chemical elements in definite proportions that cannot be separated by physical means and are held together by chemical bonds.
A chemical formula is a way of expressing information about the proportions of atoms that constitute a particularchemical compound, using a single line of chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, and plus (+) and minus (−) signs.
Current Structure of the Atom and how it differs from Older Models:
Electrons are in constant motion around the nucleus, protons and neutrons jiggle within the nucleus, and quarks jiggle within the protons and neutrons.
Plum Pudding: random electrons, no nucleus, positive field
Rutherford: random electrons, has nucleus, showed protons and neutrons
Bohr’s: electrons orbiting around, has nucleus
Electrons are in constant motion around the nucleus, protons and neutrons jiggle within the nucleus, and quarks jiggle within the protons and neutrons.
Plum Pudding: random electrons, no nucleus, positive field
Rutherford: random electrons, has nucleus, showed protons and neutrons
Bohr’s: electrons orbiting around, has nucleus
Current Atom Model: The Wave Mechanical Model
The orbitals had different shapes and maximum numbers at any level:
s (sharp) - spherical (max = 1)
p (principal) - dumb-bell shaped (max = 3)
d (diffuse) - four-lobe-shaped (max = 5)
The names of the orbitals came from names of atomic spectral features before quantum mechanics was formally invented. Each orbital can hold only two electrons.
How an element can change:
An element is determined solely by the number of protons in the nucleus of a given atom, the only way an atom can change its elemental identity is by changing the number.
The orbitals had different shapes and maximum numbers at any level:
s (sharp) - spherical (max = 1)
p (principal) - dumb-bell shaped (max = 3)
d (diffuse) - four-lobe-shaped (max = 5)
The names of the orbitals came from names of atomic spectral features before quantum mechanics was formally invented. Each orbital can hold only two electrons.
How an element can change:
An element is determined solely by the number of protons in the nucleus of a given atom, the only way an atom can change its elemental identity is by changing the number.
How an element becomes an Isotope:
When an atom is missing a neutron or has an extra neutron. That type of atom is called an isotope. The same goes for isotopes. They are still the same element. They are just a little different from every other atom of the same element.
When an atom is missing a neutron or has an extra neutron. That type of atom is called an isotope. The same goes for isotopes. They are still the same element. They are just a little different from every other atom of the same element.
Physical Properties of Metals:
Efficient conduction of heat and electricity
-Malleability (flatten into sheets
-Ductility( pulled to form a wire)
-A lustrous (shiny) appearance
Groups of Periodic Table:
The Table's pattern and arrangement reflects the arrangement of electrons in the atom. Elements have different atomic numbers - the number of protons or electrons increases up the table as electrons fill the shells. Elements have different atomic masses - the number of protons plus neutrons increases up the table. Rows - elements of each row have the same number of energy levels (shells). Columns - elements have the same number of electrons in the outermost energy level or shell (one to eight).
Efficient conduction of heat and electricity
-Malleability (flatten into sheets
-Ductility( pulled to form a wire)
-A lustrous (shiny) appearance
Groups of Periodic Table:
The Table's pattern and arrangement reflects the arrangement of electrons in the atom. Elements have different atomic numbers - the number of protons or electrons increases up the table as electrons fill the shells. Elements have different atomic masses - the number of protons plus neutrons increases up the table. Rows - elements of each row have the same number of energy levels (shells). Columns - elements have the same number of electrons in the outermost energy level or shell (one to eight).
Diatomic Molecules:
Hydrogen (H2)
Nitrogen (N2)
Oxygen (O2)
Fluorine (F2)
Chlorine (Cl2)
Iodine (I2)
Bromine (Br2)
Allotropes:
An allotrope is a variant of a substance consisting of only one type of atom. It is a new molecular configuration, with new physical properties. Substances that have allotropes include carbon, oxygen, sulfur, and phosphorous. Allotropes of a given substance will often have substantial differences between each other. For example, one allotrope of carbon, fullerene, is many times stronger and lighter than steel. An allotrope should not be confused with phase, which is a change in the way molecules relate to each other, not in the way that individual atoms bond together.
Ionic Compounds from Ions:
Ionic compounds are made when positive and negative ions come together. Their electrons are shared or transferred to form a new compound.
Hydrogen (H2)
Nitrogen (N2)
Oxygen (O2)
Fluorine (F2)
Chlorine (Cl2)
Iodine (I2)
Bromine (Br2)
Allotropes:
An allotrope is a variant of a substance consisting of only one type of atom. It is a new molecular configuration, with new physical properties. Substances that have allotropes include carbon, oxygen, sulfur, and phosphorous. Allotropes of a given substance will often have substantial differences between each other. For example, one allotrope of carbon, fullerene, is many times stronger and lighter than steel. An allotrope should not be confused with phase, which is a change in the way molecules relate to each other, not in the way that individual atoms bond together.
Ionic Compounds from Ions:
Ionic compounds are made when positive and negative ions come together. Their electrons are shared or transferred to form a new compound.
Protons, Electrons, Neutrons in an Element