chemical notation that was invented in 181 by John Jakob Berzelius. The system is based on the law of definite proportions”‚ states that all samples of a given chemical compound have the same elemental composition. It is also a way of expressing information about the proportions of atoms that constitute a particular chemical 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.
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physical property of matter‚ as each element and compound has a unique density associated with it. Density defined in a qualitative manner as the measure of the relative "heaviness" of objects with a constant volume. Pure Substances A substance with uniform composition. Cannot be separated by physical or mechanical means. Elements Cannot be broken down or changed into another substance using chemical means. *Building blocks of matter* Compounds A pure substance that is composed of two or more
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and form compounds that may have new physical and chemical properties. There are two main kinds of bonds‚ they ionic and covalent. In bonding the goal of the atoms involved is to reach a level of stability with less energy. In order to reach the epitome of stability‚ as in the case of noble gases‚ an atom strives to complete its outer shell. Either losing or gaining electrons may do this‚ which concludes in an ionic bond or the sharing of electrons with other atoms which makes a covalent bond. Ionic
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15.2 Born-Haber Cycle Our calculations of enthalpies so far have involved covalent substances. Now we need to look at the enthalpy changes involved in the formation of giant ionic lattices. Lattice enthalpy is defined as either the: ’the enthalpy change that occurs when one mole of a solid ionic crystal is broken into its ions in the gaseous state‚ at standard temperature and pressure. Because all the bonds in the ionic lattice are broken‚ it is an endothermic process‚ ∆H is positive. ’ The
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Chapter 2 Study Questions 1. Define the following a) element b) compound c) pure substance 2. Classify each of the following as a pure substance or a mixture. For each pure substance‚ indicate whether it is an element or a compound. Which of the mixtures are solutions a) air b) titanium c) oak d) baking soda e) oxygen f) 7-Up g) wine h) carbon monoxide 3. Label each of the following drawings as element‚ compound‚ or mixture (Assume each type of circle represents a different
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is made up of tiny particles and they are constantly moving/continual state of motion. 1.1.2 Identify the difference between elements‚ compounds and mixtures in terms of particle theory Elements are simplest form substance meaning cannot be decomposed further physically or chemically. They are made up of same type of atoms only e.g. helium‚ oxygen. Compounds are pure and they consist of 2 or more elements bonded chemically (fixed ratio). They can be decomposed chemically. E.g. sodium chloride
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(purple) • Left Side of PT table loses electrons‚ right side gains them. • Covalent bonds formed between different elements are polar. • In a molecule with covalent bonding‚ atoms are held together by sharing electrons. • Electronegativity (EN) measures the tendency of an atom to attract electrons (increases as you move to the right) • Greater than 1.8 = Ionic‚ Between 0 and 1.8 = Polar Covalent‚ ~0 = Nonpolar covalent • Moles = Mole * (Number of electrons in element/ 1 mole) • Atoms = Moles
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Current‚ Voltage and Power * Electricity is the flow of electric charge. We can describe the flow of electric charge in several ways. These include the quantities Current‚ Voltage and Power. Current * Current (I) is the rate of flow of Charge Carriers‚ such as electrons. Current is usually thought of as moving in the direction of positive charge‚ so from the positive power supply to the negative. However‚ since in metals it is electrons that carry electric charge‚ the actually flow is opposite
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largest Ei2 and the smallest Ei7? B largest Ei2 C smallest Ei7 Which element in each of the following sets has the smallest first ionization energy‚ which has the largest?1) Li(L)‚ Ba‚ K(S)2) B(S)‚ Be‚ Cl(L)3) Ca(s)‚ C‚ Cl(L) Order the following compounds according to their expected lattice energies: LiClKClKBrMgCl2 MgCl2>LiCl>KCl>KBr Ranked by Smallest molecules have the largest lattice energy. calculate the overall energy change in kilojoules per mole for the formation of CsF(s) from
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chlorine can displace bromine in the compound sodium bromide and make sodium chloride plus bromine.Another example is that fluorine can displace chlorine.This is how the halogens can displace each other chlorine + sodium bromide → sodium chloride + bromine Task 2 There are two types of bonding.Covalent bonding and ionic bonding. Ionic bonding occurs from positively ions and negatively ions‚which attracts each other and bind together to form ionic compounds.Each ion is surrounded by an
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