Elements, Compounds, Mixtures SUMMARY

Elements, Compounds, and Mixtures

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• Elements 1.1
• Compounds 1.2
• A closer look at atoms
• Elements Compounds and Mixtures Quiz

Caption: : The Atom theory of Matter

Elements

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Caption: : Elements can be classified as metallic and non-metallic

Elements are substances that are made up of just one type of atom. Each element has a unique set of characteristics that scientists refer to as its properties. Elements can be classified into metallic and non-metallic elements. All metallic elements -: shiny solid at room temperatures(apart from mercury) good conductors of heat and electricity malleable(bent and hammered into sheets) ductile(stretched into wires Non -metallic elements-: dull(not shiny) do not conduct heat or electricity) Break or crumble when you bend them(brittle) solid or gases at room temperature(apart from bromine) There are 118 elements, but only 91(92) occur naturally.

Atoms in Elements

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Caption: : Atoms can exist as: Monatomic, Molecular and Lattice

The way atoms are arranged in Elements determines many of the physical properties of an element. Monatomic elemets are rare, with only 6 of the 92 naturally occurring elements being monatomic. These are -: Helium, Neon, Argon, Krypton, Xenon and Radon. Molecules are cluster of two or more atoms bonded together. In a molecular element, all the molecules are identical with the same shape, size, number and types of atoms. The atoms in metals don't form molecules, but instead form large grid-like structures known as crystal lattices. In metal lattices, the atoms are only weakly joined to each other. As a result, metals can be bent into wires. In non-metallic lattices, the atoms are strongly bonded to each other. This makes them hard and brittle.

The many faces of Carbon

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Caption: : Allotropes of Carbon

Charcoal: Carbon in the form of charcoal is used for drawing because it's black and soft and crumbles easily. Graphite: The carbon atoms in graphite form layers. The layers are difficult to break but can slide over each other easily. This makes graphite an excellent lubricant. Diamond: Carbon in the form of diamond is the hardest natural substance on Earth because the bonds between the atoms are extremely strong. Carbon Fibre: Carbon fibre is very light , very strong and flexible and so is often used in sporting equipment such as the mountain bike. Nanotubes: A carbon nanotube can be thought of as a sheet of carbon rolled into a tube. These tubes are very tough so scientists are researching how to spin then into yarn to create new-age materials.

END OF ELEMENTS

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https://www.youtube.com/watch?v=NzJPRhymoY0 (Embed)

Caption: : Periodic Table

Caption: : Atoms and elements video

Compounds

Compounds are made up of more than one type of atom. Compounds have properties that are usually very different from the properties of elements. Each molecule is made by combining different numbers of the same elements, oxygen hydrogen etc. Scientists represent the molecules of compounds in a similar way to the molecules of an element. H2O indicates that there are 2 hydrogen atoms for every oxygen atom. Compounds can also form crystal lattices. In these lattices, the atoms are strongly bonded to each other so they tend to be very hard solids at room temperatures. In a lattice of sodium chloride, sodium and chloride atoms form a grid-like structure with one sodium atom for every chlorine atom.