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CHAPTER 2: THE CHEMCIAL CONTEXT OF LIFE - Coggle Diagram
CHAPTER 2: THE CHEMCIAL CONTEXT OF LIFE
Concept 2.1: Matter consists of chemical elements in pure form and in combinations called compounds
Matter is anything that occupies space and has mass. It forms the basis of all physical substances, including rocks, metals, oils, gases, and living organisms.
MATTER IS MADE UP OF ELEMENTS
ELEMENT: a substance that cannot be broken down to other substances by chemical reactions
Today, chemists recognize elements occurring in nature; gold, copper, carbon, and oxygen are examples.
humans need 25/92 elements, plant need 17/92
Just four elements—oxygen , carbon , hydrogen , and nitrogen —make up approximately of living matter. Calcium , phosphorus , potassium , sulfur ,
and a few other elements account for most of the remaining 4% or so of an organism’s mass.
Trace elements are required by an organism in only minute quantities.--INDSISPENSABLE FOR LIFE
iron is a trace element required for the proper functioning of hemoglobin, the molecule that carries oxygen in red blood cells.---A person with an iron deficiency will probably show fatigue and other effects of a low oxygen level in the blood. (The condition is called anemia and can also result from too few red blood cells or abnormal hemoglobin.) ON THE OTHER HAND, EXCESS IRN CAN CAUSE JOINT PAIN, ABDOMINAL PAIN, FATIGUE, HEART PROBLEMS, BRONZE OR GRAY TINTED SKIN
COMPOUND: A substance consisting of two or more different elements combined in a fixed ratio.
Table salt, for example, is sodium chloride , a compound composed of the elements sodium and chlorine in a ratio.
PURE SODIUM- METAL AND PURE CHLORINE- POISNOUS GAS, HOWEVER WHEN CHEMICAL COMBINED CREATES AN EDIBLE POWDER
organized matter has emergent properties: A compound has characteristics different from those of its elements
Concept 2.2: An element’s properties depend on the structure of its atoms
Each element consists of a certain type of atom that is different from the atoms of any other element.
An atom is the smallest unit of matter that retains the properties of an element.
These tiny bits of matter are composed of even smaller parts, called subatomic particles
protons:
A subatomic particle with a single positive electrical charge. # OF PROTONS DEFINES A SPECIFIC ELEMENT
with a mass of about 1.7 times 10 to the negative 24 g (APPROX 1 DALTON)
electrons:
A subatomic particle with a single negative electrical charge and a mass about 1 two-thousandths that of a neutron or proton. One or more electrons move around the nucleus of an atom.
The rapidly moving electrons form a “cloud” of negative charge around the nucleus, and it is the attraction between opposite charges that keeps the electrons in the vicinity of the nucleus.
The chemical behavior of an atom depends mostly on the number of electrons in its outermost shell, known as valence electrons.
the outermost electron shell the valence shell.
1 more item...
neutrons:
subatomic particles found in the nucleus of an atom, alongside protons-- ELECTRICALLY NEUTRAL
with a mass of about 1.7 times 10 to the negative 24 g (APPROX 1 DALTON)
ATOMIC NUCLEUS: An atom’s dense central core, containing protons and neutrons. protons give the nucleus a positive charge.
ATOMIC #: The number of protons in the nucleus of an atom, unique for each element and designated by a subscript
THE SMAL 2 @ THE BOTTOM LEFT OF He IS THE ATOMIC #- ELEMENT HELIUM HAS TWO PROTONS IN ITS NUCLEUS. Unless otherwise indicated, an atom is neutral in electrical charge, which means that its protons must be balanced by an equal number of electrons. 2 ELECTRONS.
MASS #: The total number of protons and neutrons in an atom’s nucleus, written as a superscript to the left of an element’s symbol. MASS #-ATOMIC #= NEUTRONS
ISOTOPES: One of several atomic forms of an element, each with the same number of protons but a different number of neutrons, thus differing in atomic mass
radioactive isotopes: A radioactive isotope (or radioisotope) is an unstable form of a chemical element that releases radiation
Concept 2.3: The formation and function of molecules and ionic compounds depend on chemical bonding between atoms
Now that we have looked at the structure of atoms, we can move up the hierarchy of organization and see how atoms combine to form molecules and ionic compounds.
CHEMICAL BONDS: An attraction between two atoms, resulting from a sharing of outer-shell electrons or the presence of opposite charges on the atoms. The bonded atoms gain complete outer electron shells.
A covalent bond is the sharing of a pair of valence electrons by two atoms.
Two or more atoms held together by covalent bonds constitute a molecule
Molecule: A molecule is formed when two or more atoms are covalently bonded together. These atoms can be of the same element, like in oxygen gas (O₂), or different elements, like in water (H₂O).
Atoms in a molecule attract shared bonding electrons to varying degrees, depending on the element. The attraction of a particular atom for the electrons of a covalent bond is called its electronegativity.
In a covalent bond between two atoms of the same element, the electrons are shared equally because the two atoms have the same electronegativity—the tug-of-war is at a standoff. Such a bond is called a nonpolar covalent bond.
when an atom is bonded to a more electronegative atom, the electrons of the bond are not shared equally. This type of bond is called a polar covalent bond
For example, the bonds between the oxygen and hydrogen atoms of a water molecule are quite polar
SINGLE BOND: A single covalent bond; the sharing of a pair of valence electrons by two atoms.
DOUBLE BOND: A double covalent bond; the sharing of two pairs of valence electrons by two atoms.
Oxygen has 6 electrons in its second electron shell and therefore needs 2 more electrons to complete its valence shell. Two oxygen atoms form a molecule by sharing two pairs of valence electrons. THE ATOMS ARE FORMED BY A DOUBLE BOND.
VALENCE FOR OXYGEN = 2 (VALANCE--The bonding capacity of a given atom; the number of covalent bonds that an atom can form, which usually equals the number of unpaired electrons in its outermost (valence) shell.)
Covalent bonds involve the sharing of electrons between atoms, allowing them to complete their valence shells. These bonds are strong and form molecules. For instance, two hydrogen atoms share electrons to form a single covalent bond, while two oxygen atoms share two pairs of electrons to form a double covalent bond. The shared electrons create a stable connection between the atoms.
Ionic bonds occur when atoms transfer electrons due to a significant difference in electronegativity. This results in the formation of ions cations (positively charged) and anions (negatively charged).
For example, when sodium (Na) transfers an electron to chlorine (Cl), sodium becomes a cation, and chlorine becomes an anion. The attraction between these oppositely charged ions forms an ionic bond. Ionic bonds are strong in dry compounds but weaker in aqueous solutions.
Hydrogen bond: A type of weak chemical bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule or in another region of the same molecule.
occurs when a hydrogen atom, which is covalently bonded to a more electronegative atom like oxygen or nitrogen, experiences an attraction to another electronegative atom nearby
They have a specific direction, which affects the shape and properties of molecules
In water, hydrogen bonds are responsible for its high boiling point and surface tension.
Hydrogen bonds are weaker than covalent and ionic bonds but are crucial for the structure and properties of many compounds.
Van der Waals interactions are weak forces that occur between molecules or atoms when they are very close together.
These interactions arise because electrons are not always evenly distributed around a molecule, leading to temporary regions of positive and negative charges.
Although each interaction is weak, collectively they can be significant. For example, the gecko lizard can walk up walls due to numerous van der Waals interactions between its foot molecules and the wall's surface molecules
These interactions are crucial in biological systems, helping to maintain the structure of large molecules like proteins and nucleic acids by reinforcing their three-dimensional shapes.
Concept 2.4: Chemical reactions make and break chemical bonds
The making and breaking of chemical bonds, leading to changes in the composition of matter, are called chemical reactions.
An example is the reaction between hydrogen and oxygen molecules that forms water
Reactants are substances that undergo change during a chemical reaction. They are present at the beginning of the reaction and are transformed into products. For example, in the reaction where hydrogen molecules (H₂) react with oxygen molecules (O₂) to form water (H₂O), hydrogen and oxygen are the reactants. This transformation involves breaking and forming chemical bonds, but the atoms themselves are not created or destroyed.
In this reaction, the reactants (hydrogen and oxygen) are converted into products (water), demonstrating the conservation of matter. Atoms are not created or destroyed but are rearranged. This principle is crucial in understanding processes like photosynthesis, where carbon dioxide and water are converted into glucose and oxygen, powered by sunlight. This rearrangement of atoms is fundamental to life, providing food and oxygen for living organisms.
PRODUCT: A material resulting from a chemical reaction, SUCH AS WATER
CHEMICAL EQUILIBRIUM: In a chemical reaction, the state in which the rate of the forward reaction equals the rate of the reverse reaction, so that the relative concentrations of the reactants and products do not change with time
At equilibrium, the forward and reverse reactions occur at the same rate.