• 6-8: 4D/M1a. All matter is made up of atoms, which are far too small to see directly through a microscope.
• 6-8: 4D/M1b. The atoms of any element are like other atoms of the same element, but are different from the atoms of other elements.
• 6-8: 4D/M1cd. Atoms may link together in well-defined molecules, or may be packed together in crystal patterns. Different arrangements of atoms into groups compose all substances and determine the characteristic properties of substances.
• 6-8: 4D/M5. Chemical elements are those substances that do not break down during normal laboratory reactions involving such treatments as heating, exposure to electric current, or reaction with acids. All substances from living and nonliving things can be broken down to a set of about 100 elements, but since most elements tend to combine with others, few elements are found in their pure form.
• 6-8: 4D/M6a. There are groups of elements that have similar properties, including highly reactive metals, less-reactive metals, highly reactive nonmetals (such as chlorine, fluorine, and oxygen), and some almost completely nonreactive gases (such as helium and neon).
• 6-8: 4D/M10. A substance has characteristic properties such as density, a boiling point, and solubility, all of which are independent of the amount of the substance and can be used to identify it.
• 6-8: 4D/M11. Substances react chemically in characteristic ways with other substances to form new substances with different characteristic properties.
• 6-8: 4D/M12. If samples of both the original substances and the final substances involved in a chemical reaction are broken down, they are found to be made up of the same set of elements.
• 9-12: 4D/H2. The number of protons in the nucleus determines what an atom's electron configuration can be and so defines the element. An atom's electron configuration, particularly the outermost electrons, determines how the atom can interact with other atoms. Atoms form bonds to other atoms by transferring or sharing electrons.
• 9-12: 4D/H3. Although neutrons have little effect on how an atom interacts with other atoms, the number of neutrons does affect the mass and stability of the nucleus. Isotopes of the same element have the same number of protons (and therefore of electrons) but differ in the number of neutrons.
• 9-12: 4D/H6. When elements are listed in order by the masses of their atoms, the same sequence of properties appears over and over again in the list.
• 9-12: 4D/H7a. Atoms often join with one another in various combinations in distinct molecules or in repeating three-dimensional crystal patterns.

• 9-12: 4G/H3. Most materials have equal numbers of protons and electrons and are therefore electrically neutral. In most cases, a material acquires a negative charge by gaining electrons and acquires a positive charge by losing electrons. Even a tiny imbalance in the number of protons and electrons in an object can produce noticeable electric forces on other objects.

This resource has the added feature of displaying elements in tabs at the top of the web page. It is quite easy for learners to compare various elements without toggling among different windows or browser tabs. Click on any element to view physical properties, atomic structure, background information, and images. Selected elements feature videos that show reactions among common elements.

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