Atoms/Molecules
Here are some basic facts about atoms.
*All atoms are made of three basic particles: protons (they have a positive charge), neutrons (they have no charge - they are neutral), and electrons (they have a negative charge).
*Protons and neutrons are found together in the atoms nucleus,and electrons orbit around the nucleus in an electron cloud.
*The electrons orbit in areas called "shells." Each shell can hold a certain number of electrons. The first shell in any atom can hold only up to two electrons. The second shell can hold up to 8 electrons. There are more shells found in some atoms, and each shell holds up to a certain number of electrons.
*Scientists used to believe that protons, neutrons and electrons were the smallest particles of matter. However, they discovered that inside protons and neutrons were even smaller particles that they called "quarks". The quarks inside the protons or neutrons are held together by "gluons."
*Protons and neutrons have about the same mass (which is like its weight).
*The number of Protons that an atom has tells what kind of atom (element) it is. For example, all oxygen atoms have 8 protons. All stable atoms has the same number of protons (with a positive charge) and electrons(with a negative charge). So an oxygen atom has 8 protons and 8 electrons. An atom usually has the same number of neutrons as it does protons.
*Electrons can be stripped off of or added to atoms to give the atom a positive or negative charge. Then the atom is called an ion. For example, if the oxygen atom has 8 protons (all with +positive charges), but it has an electron removed so that there are only seven electrons (all with - negative charges) then the atoms has one extra positive charge and it is called an oxygen ion.
*Neutrons can be added or subtracted from an atoms and that changes the mass (weight) of the atom. Then it is called an "isotope" It does not change the kind of atom. For example, isotopes of Oxygen can have 8 protons, 8 electrons and 9 neutrons, which would make the atom a heavier version of oxygen.
*When atoms that are all the same kind bond together, then the result is an element. For example Gold is an element because it is made up only of gold atoms bonded together
*When atoms from different elements bond together, then molecules are formed. The atoms in these molecules bind together chemically (usually by sharing electrons) and the new molecule acts differently than the atoms it was made from. For example, a water molecule is made up of two Hydrogen atoms (Hydrogen has 1 Proton) and one Oxygen atoms (8 protons). A water molecule is not just three atoms mixed together - the two hydrogens and the oxygen bind to each other to form something that is very different from the elements of Hydrogen and Oxygen. The symbol for water is H2O because it means H - Hydrogen 2atoms of it, and O - Oxygen.
It has been very interesting learning about atoms and molecules. I've also had a chance to build some models of atoms and molecules to help me understand better. It's amazing to think that everything around us is made up of these tiny particles that are too small to be seen even with the most powerful microscopes!
Marco Polo
On the way, the group of travelers was attacked by robbers. In the Gobi Desert, Marco became separated and lost from the others. Luckily, Marco finally found his group, but he fell ill from not having enough water and from breathing too much sand. Their guide told them to travel up the mountains where the air was pure. Even though the trip up the mountains was difficult, Marco felt better the higher the group climbed. When they group reached the top, Marco was completely cured!
Marco's father had met the Khan (ruler) of China on his other trip, and when the explorers arrived at the Khan's palace, the Khan held a great feast in their honor. The Khan asked Marco to explore the unknown parts of the kingdom. While Marco was exploring, he encountered big cats with spots (cheetahs), men with tails (orangutans), and logs with eyes (crocodiles). His explorations helped map much of China. After Marco was in China for 25 years, the Khan became very sick and told Marco to leave China for his own safety. The Khan gave Marco a big chest of jewels and treasure.
After Marco returned to Venice, there was a war with Genoa and Marco was captured. The Dutchess of Genoa had heard of Marco. She visited him in jail and asked him to tell all of his adventures. She thought he was a very good story teller. Marco's friend in the jail wrote down his story and made it into a book: The Travels of Marco Polo. This book was inspiring to young explorers all through the rest of the Middle Ages and through the Renaissance.
