Define element, atom, compound, molecule, and trace element. ELEMENT: a substance that cannot be broken down to other substances by chemical reactions.
COMPOUND: a substance consisting of two or more elements combined in a fixed ratio. MOLECULE: two or more atoms held together by covalent bonds TRACE ELEMENTS: those required by an organism in only minute quantities. Give the mass, charge, and location of each sub-atomic particle. Mass= 1 Dalton or 1.009 grams or 1.7 x 10-24
Mass= 1 Dalton or 1.007 grams or 1.7 x 10-24 Mass= we ignore the mass of an electron Location=moving nearly at the speed of light, electrons form a cloud around the nucleus. Define and use atomic number and atomic mass number. ATOMIC NUMBER: the number of protons in an element. Is written as a subscript to the left of the symbol for the element. ATOMIC MASS NUMBER: the sum of protons plus neutrons in the nucleus of an atom. The mass number is written as a superscript to the left of an element?s symbol. Explain why isotopes have similar chemical and therefore biological properties. How are isotopes used by biologists? Radioactive isotopes in particular have many useful applications in biology. Radioactive isotopes date fossils, are used as tracers to follow atoms through metabolism, and are helpful in diagnosing kidney disorders. Describe the relative energy of electron shells. FIRST ENERGY LEVEL (shell): closest to the nucleus and has the lowest energy. SECOND ENERGY LEVEL (shell): more energy…. THIRD ENERGY LEVEL (shell): more energy Describe the placement of electrons into the 1s, 2s, and 2p orbitals? No more than two electrons can occupy the same orbital.
The Essay on Atomic Mass Element Atoms Metals
Chapter Three Summary: Atoms and atom's structure Ancient Greek Philosophers suggested that matter was composed of individual particles, which was proved by the theory of John Dalton. The main provisions of his theory are: 1. All matter is composed of tiny, indivisible particles called atoms. 2. All atoms of a particular element are identical but the atoms of one element differ from the atoms of ...
1s-The first energy shell has a single orbital and can thereby accommodate a maximum of two electrons. This orbital is spherical in shape. The lone electron of a hydrogen atom occupies the 1s orbital, as do the two electrons of a helium atom. *Electrons like all matter tend to exist in the lowest available state of potential energy. 2s-The second electron shell can hold eight electrons, two in each of the four orbitals. Electrons in the four different orbitals all have nearly the same energy, but they move in different volumes of space. The 2s orbital is spherical in shape, but of a greater diameter than the 1s orbital.
2p-The other three orbitals, are dumbbell-shaped, each oriented at right angles to the other two. At higher energy levels these orbitals are referred to as 3s, 3p, and so on. **see fig. 2.8 page 27 ***Valence electrons-the chemical properties of an atom depend mostly on the number of electrons in its outermost shell; these outermost electrons are referred to as valence electrons, and the outermost shell as the valence shell.
Each atom that can share valence electrons has a bonding capacity corresponding to the number of covalent bonds the atom can form. When the bonds form, the give the atom a full complement of valence electrons. This bonding capacity is called the atom?s valence and equals the number of unpaired electrons in the atom?s outermost (valence) shell. **Since electrons tend to exist in their lowest state of potential energy multiple electron shells exist. We can readily determine the valences of many elements from their electron configurations. The valence of hydrogen is 1; oxygen , 2; nitrogen, 3; and carbon, 4. Biologically important molecules generally have a valance of 5, forming three single bonds and one double bond. Of the first 18 elements, only helium, argon, and neon have atoms with full valence shells; these elements are called inert because they are unreactive. **see fig. 2.9 page 28 List the 6 main covalently bonding atoms and 5 main ions. Give each its appropriate symbol – with valence or ionic indicated. ion- an atom that has gained or lost electrons, thus acquiring a charge. cation- an ion with a positive charge, produced by the loss of one or more electrons.
The Essay on Amino Acid Atoms Bonds Hydrogen
Chapters 2 & 3 Study Guide (Chapter 2) Atoms: Consist of Protons (+), Neutrons, and Electrons (-) - Number of Protons = Number of Electrons - Protons + Neutrons = Mass Number - Number of Protons = Atomic Number Isotopes: Same number of protons but different number of neutrons - All isotopes of an element interact with other atoms in the same way Orbitals: - Can house 1 or at most 2 electrons - ...
What determines the number of covalent bonds that form? The number of electrons required to complete required to complete an atom?s valence shell determines how many bonds that atom will form. If two unattached hydrogen atoms meet, they can form a single covalent bond. **see fig. 2.10 page 29 Redraw these molecular formulas as structural formulas. How does molecular shape emerge from orbital chemistry? Molecular shape is due to hybrid orbitals. The four teardrop-shaped orbitals of a valence shell involved in covalent bonding form by hybridization of the single s and three p orbitals. **see fig. 2.15 page 32 The role of molecular shape is the correlation between structure and function, one of biology?s unifying themes. Define electronegativity, polar covalent bond, and nonpolar covalent bond? Electronegativity- the tendency for an atom to pull electrons toward itself. Polar covalent bond- a type of covalent bond between atoms that differ in electronegativity; the shared slightly positive. Nonpolar covalent bond- a type of covalent in which electrons are shared equally between two atoms of similar electronegativity. Explain the chemical basis of the weak bonds: ionic, hydrogen, Van der Waals, and hydrophobic.
Ionic- because of their opposite charges, cations and anions attract each other in ionic bonds. Ionic compounds are also called salts. Hydrogen- If a water molecule and an ammonia molecule are close together, a weak attraction will occur between the negatively charged nitrogen atom and a positively charged hydrogen atom of the adjacent water molecule. This attraction is a hydrogen bond. Van der Waals- Because electrons are in constant motion they may accumulate by chance in one part of the molecule or another. The results are ever-changing ?hot spots? of positive and negative charge that enable all atoms and molecules to stick to one another. These Van der Waals interactions are weak and only occur when atoms and molecules are very close together. Define chemical reaction, reactant, and product. Chemical reaction-the making and breaking of chemical bonds, leading to changes in the composition of matter Product-is to the right of the equation How do concentrations of reactants and products affect rate? The greater the concentration of reactant molecules, the more frequently they collide with one another and have an opportunity to react to form products. As products accumulate, collisions resulting in the reverse action. Show the development of chemical equilibrium using given rate constants. Chemical equilibrium is reached when the forward and reverse action rates are equal.
The Essay on Covalent Bond Atoms Groups Molecules
Bio-molecules are built by assembling atoms, by virtue of covalent bonds. The most collective elements that can be discovered in bio molecules are the CHOPS element, which stands for the basic abbreviation of carbon, hydrogen, nitrogen, phosphorus, and sulfur. Each one of these elements has a specific valence. A valence resolves the number from the covalent bonds it can be able to form. Presuming ...
