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  1. 5. The electron affinity of an atom or molecule is defined as the amount of energy released when an electron is attached to a neutral atom or molecule in the gaseous state to
  2. 6. A chemical property is any of a material's properties that becomes evident
  3. 13. Elements Table.
  4. 14. after, a chemical reaction; that is, any quality that can be established only by changing a
  5. 15. have relatively low attraction for electrons, as indicated by their low electronegativities.
  6. 17. number and the distance at which its valence electrons reside from the charged nucleus.
  7. 18. the neutron is a subatomic particle, symbol n or n0 , which has a neutral charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms.
  8. 20. the nucleus is a membrane-bound organelle that contains genetic material (DNA) of eukaryotic organisms. As such, it serves to maintain the integrity of the cell by facilitating
  9. 21. a metalloid is a type of chemical element which has a preponderance of properties in between,or that are a mixture of, those of metals and nonmetals. There is no standarddefinition of a metalloid and no complete agreement on which elements are metalloids.
  10. 23. The atomic radius of a chemical is a measure of the size of its atoms, usually the mean or typical distance from the center of the nucleus to the boundary of the surrounding shells of electrons.
  11. 25. the fixed amount of energy that a system described by quantum mechanics, such as a molecule, atom, electron, or nucleus, can have.
  12. 26. Atomic theory is the scientific theory that matter is composed of particles called the atomic number The number of protons in the nucleus of an atom, which determines the chemical properties of an element and its place in the periodic table.
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  1. 1. in chemistry, an element is a pure substance consisting only of atoms that all have the same numbers of protons in their atomic nuclei. Unlike chemical compounds, chemical elements cannot be broken down into simpler substances by chemical means.
  2. 2. refers to the level of reactivity of a metal. Metals tend to lose electrons in chemical reactions, as indicated by their low ionization energies. Within a compound, metal
  3. 3. in chemistry, a group is a column of elements in the periodic table of the chemical elements.there are 18 numbered groups in the periodic table; the f-block columns are not helium vs. hydrogen in Hindenburg-Hydrogen is the earth's lightest element, and it can be obtained easily and inexpensively, but its flammability makes it unacceptable for manned airship operations.while the use of helium presented obvious operational challenges, airships of sufficient size were able to operate effectively when inflated with helium.
  4. 4. of the entire cell volume.
  5. 7. The basic unit of a chemical element.
  6. 8. a chemical element that constitutes 21 percent of the Earth's atmosphere,that is capable of combining with all elements except some noble gases, that is active in physiological processes of almost all known organisms, and that is involved especially in combustion — see
  7. 9. The mass of an atom of a chemical element expressed in atomic mass units, It is approximately equivalent to the the number of protons and neutrons in the atom.
  8. 10. the number of electrons in the outermost shell of a particular atom
  9. 11. and replication processes. It's the largest organelle inside the cell taking up about a
  10. 12. electronegativity, symbolized as χ, is the measurement of the tendency of an atom to attract a shared pair of electrons. An atom's electronegativity is affected by both its
  11. 14. its reactivity tendency to form chemical bonds with other atoms. This outermost shell is known as the valence shell, and the electrons found in it are called valence electrons.
  12. 16. chemical identity.
  13. 19. a stable subatomic particle with a charge of negative electricity, found in all atoms acting as the primary carrier of electricity in solids.
  14. 21. the chemical element of atomic number 80, a heavy silvery-white metal which is liquid at ordinary temperatures.
  15. 22. a negative ion.
  16. 24. Any of several forces, especially the ionic bond, covalent bond, and metallic bond,by which atoms or ions are bound in a molecule or crystal.