25. from left to right across a period in the periodic table, elements become less and more in their properties. 26. francium has 36 isotopes, but only francium-223 occurs in nature. francium-223 spontaneously emits particles and energy, so francium-223 is a(an) of francium. 27. at sea level, water at 100°c. 28. cooking requires continuous addition of energy to the chemical reactions that are taking place. the chemical reactions involved in cooking can be described as 29. the theory of matter states that all particles of matter are in constant motion. 30. in rutherford’s experiments, some of the aimed at gold atoms bounced back, suggesting that a solid mass was at the center of the atom. 31. you are given the melting points of three unknown substances and are asked to predict which one is an ionic compound. you would select the compound with the melting point. 32. a flight simulator that astronauts prepare for a shuttle launch is an example of a(an) 33. in the symbol ■([email  protected]) he, the superscript 4 is the for helium, and the subscript 2 is the for helium.

25. From left to right across a period in the periodic table, elements become less electropositive and more electronegative in their properties. 

26. Francium has 36 isotopes, but only francium-223 occurs in nature. Francium-223 spontaneously emits particles and energy, so francium-223 is a(an) radioisotope of francium. 

27. At sea level, water boils at 100°C. 

28. Cooking requires continuous addition of energy to the chemical reactions that are taking place. The chemical reactions involved in cooking can be described as endothermic. 

29. The Kinetic theory of matter states that all particles of matter are in constant motion. 

30. In Rutherford’s experiments, some of the alpha particles aimed at gold atoms bounced back, suggesting that a solid mass was at the center of the atom. 

31. You are given the melting points of three unknown substances and are asked to predict which one is an ionic compound. You would select the compound with the highest melting point. 

32. A flight simulator that helps astronauts prepare for a shuttle launch is an example of a(an) _scientific model. 

33. In the symbol 

whats the meaning of /

vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.