The Atom:
The basic unit of chemistry is the ATOM. The dense core in the middle of the atom is called the NUCLEUS, and it consists of PROTONS (positively-charged particles) and NEUTRONS (neutral-charged particles), surrounded by a cloud of ELECTRONS (negatively-charged particles) that orbit around the nucleus. The ATOM is the smallest entity that can be investigated for its chemical properties, including:
IONS:
An ion is an atom with a charge (positive or negative).
- electronegativity
- oxidation state
- ionization potential
- types of bonds that will form:
- ionic
- covalent
- hydrogen
IONS:
An ion is an atom with a charge (positive or negative).
- Anion: negatively charged ion
- Cation: positively charged ion
The Element:
An ELEMENT can be defined as a pure chemical substance that is made up of one single type of atom. It is characterized by the following:
Chemical elements are represented on a table known as the PERIODIC TABLE OF ELEMENTS.
- number of PROTONS in its nucleus
- this is called the ATOMIC NUMBER
- the MASS NUMBER, which is the SUM of the number of protons AND neutrons in the nucleus
- the ATOMIC MASS, which is the SUM of the number of protons AND neutrons in the nucleus AND electrons surrounding the nucleus
Chemical elements are represented on a table known as the PERIODIC TABLE OF ELEMENTS.
Isotopes and Radioactive Isotopes:
An isotope is a variation of a single chemical element. It has a different number of neutrons in its nucleus. This means that each isotope of an element has a different mass number, but they all have the same atomic number (number of protons). There are stable isotopes and unstable (radioactive) isotopes. One of the best examples of a stable isotope is Hydrogen. Hydrogen-1 simply has one proton in its nucleus, but no neutrons. Hydrogen-2 has 1 proton and 1 neutron in its nucleus. Hydrogen-3 has 1 proton but 2 neutrons in its nucleus. Each isotope of hydrogen has 1 electron orbiting its nucleus. Carbon-12, Carbon-13 and Carbon-14 are other well-known, stable isotopes of carbon. Carbon-12 is the most common form found on the Earth.
Radioactive (unstable) isotopes, also referred to as radioisotopes or radionuclides, decay and breakdown, releasing radioactive materials. Carbon-14 is a radioactive isotope, whereas Carbon-12 and Carbon-13 are stable. Some occur naturally, others occur as a result of nuclear fission, and some are synthetic. Radioactive isotopes have some practical uses, including nuclear power plants to power electricity, radioactive tracers in medicine for scans to see inside the body (P.E.T.), research to watch processes within the body, sterilization processes in the medical field, radioisotope thermoelectric generators, tracers to study pollutants, surface water movement, measurement of runoff, flow rates of rivers and streams, approximate aging of rocks and minerals and fossils in geology, and many other things. We even have a radioactive isotope, Americium-241, in our smoke detectors in our homes and businesses!
Positron Emission Tomography, or P.E.T. scan, uses fluorine-18 radioactive tracer as the most common radioactive isotope used in the scanning method, which is used to observe metabolic processes in the human body and aids in the diagnosis of disease.
Radioactive (unstable) isotopes, also referred to as radioisotopes or radionuclides, decay and breakdown, releasing radioactive materials. Carbon-14 is a radioactive isotope, whereas Carbon-12 and Carbon-13 are stable. Some occur naturally, others occur as a result of nuclear fission, and some are synthetic. Radioactive isotopes have some practical uses, including nuclear power plants to power electricity, radioactive tracers in medicine for scans to see inside the body (P.E.T.), research to watch processes within the body, sterilization processes in the medical field, radioisotope thermoelectric generators, tracers to study pollutants, surface water movement, measurement of runoff, flow rates of rivers and streams, approximate aging of rocks and minerals and fossils in geology, and many other things. We even have a radioactive isotope, Americium-241, in our smoke detectors in our homes and businesses!
Positron Emission Tomography, or P.E.T. scan, uses fluorine-18 radioactive tracer as the most common radioactive isotope used in the scanning method, which is used to observe metabolic processes in the human body and aids in the diagnosis of disease.
The Periodic Table of Elements:
The Periodic Table of Elements places elements in order by ATOMIC NUMBER. It is arranged by GROUPS (COLUMNS) and PERIODS (ROWS). Elements are also ordered according to their electron configuration and chemical properties. The first Periodic Table of Elements was developed by the Russian chemist Dmitri Mendeleev in 1869.
GROUPS:
According to their shared physical and chemical properties, elements can be categorized into three broader categories:
a) METALS
PERIODS:
GROUPS:
- There are 18 groups:
- Hydrogen and the Alkali Metals (Group 1)
- Alkali Earth Metals (Group 2)
- Transition Metals (Groups 3-12)
- Boron (Group 13)
- Carbon (Group 14)
- Nitrogen (Group 15)
- Oxygen (Group 16)
- Halogens (Group 17)
- Noble Gases (Group 18)
According to their shared physical and chemical properties, elements can be categorized into three broader categories:
a) METALS
- Shiny
- Great conductors of electricity
- Solids
- Form alloys with other metals
- Can form salt-like ionic compounds with other nonmetals
- Intermediate or mixed properties sandwiched between metals and nonmetals
- Most are colorful or colorless gases
- Some are insulators
- Covalently bond with other nonmetals
PERIODS:
- There are 8 periods
Chemical Bonds:
A chemical bond is an attraction between atoms, elements, molecules and compounds. They range from very strong to very weak. Bonds may form due to electrostatic attraction between ions of opposite charges, which give (donate) and/or take (receive) electrons, or through the sharing of electrons, or through an electrostatic force. The electrons in the outermost shell, or valance electrons, determine the properties and bonding of the atoms, elements, molecules or compounds.
There are several types of bonds, which include the following:
I. Covalent Bonds
II. Ionic Bonds
III. Hydrogen Bonds
IV. Van der Waal Forces
There are several types of bonds, which include the following:
I. Covalent Bonds
- The strongest type of bond
- Involves the sharing of electrons
- When the bond is formed, energy is released
- When the bond is broken, energy is consumed
- Polar Covalent Bond
- one or more electrons are unequally shared
- Nonpolar Covalent Bond
- one or more electrons are equally shared
II. Ionic Bonds
- The electrons are not shared, rather they are transferred from one atom to another
- One atom donates one or more electrons, whereas the other atom receives one or more electrons
- Atoms become positively or negatively charged ions
- Anion: negatively charged ion
- Example: Chloride (Cl-), one of the electrolytes
- Cation: positively charged ion
- Examples: Potassium (K+), Magnesium (Mg+), Sodium (Na+), Calcium (Ca+), several of the electrolytes
- Anion: negatively charged ion
- Bonds are strong, but brittle
III. Hydrogen Bonds
- Weak bonds on their own, but collectively strong
- The bonds found between water molecules
- Give water its surface tension and ability to "bend" or form droplets and hold their shape
- Easily break, then reform
- Partially electrostatic attraction between a hydrogen (H+) atom and a more electronegative oxygen (O) or nitrogen (N) or fluorine (F) atom
IV. Van der Waal Forces
- These are simply weak attractions between atoms or molecules
- These types of weak interactions are some of the attractions that hold together the DNA molecule, creating its unique coil shape
- These interactions aid in the 3-D and 4-D coiling shapes of large macromolecules, such as proteins (myoglobin, hemoglobin)
- Van der Waal Forces are seen in nature, as they aid in the "sticky feet" of Gecko lizards and their ability to climb surfaces without falling off
Ionic Bonds:
Covalent Bonds:
Hydrogen Bonds:
Van der Waals Forces:
Surface Tension:
Surface tension is the tendency of a liquid to show elastic properties, or "bendable" properties. This is why water is able to form a droplet and hold its form, hold onto the faucet for awhile before it drips down, why water bugs (water striders) are able to stand on the surface of the water without sinking, why the oil in lava lamps forms its shape and stretches before breaking, and how wine forms drips called "tears of wine" on the inside surface of a wine glass.
Surfactants, found in dishwashing liquid, soap, and laundry detergent, lower the surface tension, which is the process behind the lifting of stains and dirt and other materials from fabrics and dishes.
Surfactants, found in dishwashing liquid, soap, and laundry detergent, lower the surface tension, which is the process behind the lifting of stains and dirt and other materials from fabrics and dishes.