molecules in liquid state‚ therefore is not an electrical conductor 1 1993 - 4(a) Marking Scheme (i) Group II/ 2 Because W has 2 electrons in its outer/ outermost shell/ W is magnesium (Mg) 1 1 (ii) (1) X is the cation/ an ion of W/ W and X are atom and ion of the same element 1 (2) Oxidation of W‚ e.g.‚ reacting W with dil. acid/ reacting W steam/ burning of W in air/ reacting W with chlorine 1 (iii) (1) 1 (2) Yes‚ because Y and Z have the same electron structure/ are the same element/
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Assignment Chapter 2 Concept Explorations 2.25. Average Atomic Mass Part 1: Consider the four identical spheres below‚ each with a mass of 4.00 g. a. Calculate the average mass of a sphere in this sample. (4.00 + 4.00 + 4.00 + 4.00)/4= 16.00/4= 4.00g Part 2: Now consider a sample that consists of four spheres‚ each with a different mass: blue mass is 4.00 g‚ red mass is 3.75 g‚ green mass is 3.00 g‚ and yellow mass is 1.25 g. * a. Calculate the average mass of a sphere in this sample
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Born-Oppenheimer approximation. Along with nuclear dynamics problem‚ electronic structure problem is one of the two steps to study quantum mechanical motion of a molecular system. Except for a small number of simple problems such as hydrogen-like atoms‚ the solution of electronic structure problems require modern computers. Electronic structure problem is routinely solved with quantum chemistry computer programs. Electronic structure calculations rank among the most computationally intensive tasks
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2 The Components of Matter Elements‚ Compounds‚ and Mixtures: An Atomic Overview An element consists of only one kind of atom. An element is one kind of substance – the composition is fixed. Each element is unique because the properties of its atoms are unique. Molecules are structures containing two or more atoms chemically bound together. Diatomic molecules are two-atom molecules such as elemental oxygen. A compound is a type of matter in which two or more different elements are chemically bonded
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STRUCTURE OF ATOMS -arrangement of atoms’ electrons -the number of electrons in an atom -distribution of electrons around the nucleus and their energies • ATOMS *Billiard Ball Model (JOHN DALTON) *Plum Pudding Model (JOSEPH J. THOMPSON) *RUTHERFORD’s Model of Atom -atoms are tiny‚ hard‚ indivisible spheres -electrons (negative charge) occupy the atom - Atom is mostly empty space with a dense nucleus • PROBLEMS with Rutherford’s Model *According to laws of physics‚ Rutherford’s atom should
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4.1 Defining the Atom Overview cannot be seen w/ naked eye def. smallest particle of an element that retains its identity in a chemical reaction Democritus’ Atomic Philosophy Democritus (460 BC- 370 BC) was a Greek philosopher first suggested the existence of atoms said they were indivisible and indestructible did not explain chemical behavior did not use scientific method John Dalton (1766-1844) English chemist schoolteacher used experimental methods he transformed Democritus’ ideas
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Mastering Concepts 2.1 1. Which chemical elements do organisms require in large amounts? Carbon‚ oxygen‚ hydrogen‚ nitrogen‚ sulfur‚ and phosphorus are the chemical elements that organisms require in large amounts. 2. Where in an atom are protons‚ neutrons‚ and electrons located? An atom’s protons and neutrons are in its nucleus. A cloud of electrons surrounds the nucleus. 3. What does an element’s atomic number indicate? An atom’s atomic number indicates the number of protons in its nucleus
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block an atom (meaning not divisible). Democritus believed that everything around us such as metal‚ water‚ and wood were atoms‚ but Dalton believed and proved that it could be more basic than that. He started thinking of compounds such as water‚ salt‚ or wood; that they could be a number of atoms combined to make that product. He also believed that atoms such as carbon‚ gold‚ and hydrogen could not be broken down. Dalton made some rules according to his theory: 1. All elements are made of atoms. 2.
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Module 16 Notes Reduction/Oxidation Reactions • Oxidation number: The charge that an atom in a molecule would develop if the most electronegative atoms in the molecule took the shared electrons from the less electronegative atoms. • Oxidation numbers are not real; they are only based on assumptions. They are useful bookkeeping tools though‚ and can help us keep track of electrons during a reaction. • The sum of all oxidation numbers in a molecule must equal the charge of that molecule. • Rules
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electrons of two different atoms. This attraction results in the two atoms binding together. An ionic bond‚ also called an electron-transfer bond‚ is a type of chemical bond that is a result of the electromagnetic attraction between ions of opposite charges‚ i.e.‚ a cation (a positively charged ion) and an anion (a negatively charged ion). An ion is an atom or group of atoms that has acquired an electrical charge due to the loss or gain of electrons. In an ionic bond‚ an atom gives or receives electrons
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