Earth Shudders What is an earthquake? An earthquake is the shaking of the ground. Some earthquakes are so mild that they go unnoticed but some are so violent they can shake down mountains and destroy cities. Many things can set off small earthquake from the rumbling of heavy traffic to the eruption of a volcano. But the biggest earthquakes are set off by the trembling of the tectonic plates that make up the Earth's surface as they grind slowly together underground . What causes earthquakes? The tectonic plates are sliding past each other all the time but sometimes they jam. Then the rock bands and stretches for a while until the strain gets so much that it snaps and the plates lurch on again. The snapping or the rock and sudden jolting of the plates sends shock waves out in all directions. When these waves reach the surface, they create earthquakes. What is focus and epicenter? The starting point of an earthquake inside the Earth is called the hypocenter or f...
Tiny Wonders What is an Atom? ATOMS ARE THE VERY SMALL BITS or particles of the thing of which any substance is made. They are too small to be seen. Two billion atoms would fit on the dot that is on the top of this 'i'. Scientists earlier thought atoms were the tiniest things in the universe, like hard balls that could never be split or destroyed. But now, they know that atoms are more like clouds of energy, mostly empty space, containing even tinier sub-atomic' particles. Inside an atom At the center of every atom, there is a dense core or 'nucleus' having two kinds of tiny particles protons and neutrons. Around the nucleus, there are even tinier particles called electrons that move around at the speed of light. Size of atoms Atoms weigh about 100 trillionths of a trillionth of a gram and are about a ten-millionth of a millimeter big. The smallest atoms are the hydrogen atoms. Helium nucleus One of the smallest nuclei of an atom is that of an at...
Elements in groups and periods There are just about 120 known components. For instance, you are comprised of billions of billions of particles yet you . Elements CHEMICAL ELEMENTS ARE those substances that cannot be split up into other substances. For example, gold cannot be split but water can be split into the elements hydrogen and oxygen. Each element is made up of atoms with fixed number of protons in their nucleus. Atoms of gold have 79 protons in their nucleus while atoms of hydrogen have 1.- Elements in groups and periods Number of elements There are about 85 naturally occurring elements. But scientists have discovered about 25 more, making the total number of identified Elements in groups and periods is , 112. Periodic table Periodic table is a chat devised by John Dalton (1766-1844) on which all the elements can be arranged according to the number of protons in the nucleus. The columns in the table are called Groups, and the rows are called Periods. Each per...
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