Preguntas
1.Explicar con sus palabras en que se diferencian la tabla periódica de Mendeleiev y la tabla periódica actual.
2. Investigar que elementos se encuentran libres, es decir, sin combinar, en la naturaleza.
3. ¿Qué elementos se encuentran libres, es decir, sin combinar en nuestro hogar? Ilustrar.
4. ¿Por qué creen que a los científicos les resulto difícil descubrir nuevos elementos?
5. Investigar cual fue el aporte de Marie Curie a la ciencia y por lo cual fue acreedora de un premio Nobel. Incluir ilustaciones.
6. Explicar por qué les parece que el concepto de peso atómico fue reemplazado por masa atómica.
7. Explicar con sus palabras que es la energía de ionización. ¿Cómo crece o disminuye en la tabla periódica?
8. Explicar con sus palabras que relación tienen la energía de ionización y la electronegatividad.

Ayudenme plsss

In an experiment examining the effects tai chi on arthritis pain, callahan (2010) selected a large sample of individuals with doctor-diagnosed arthritis. half of the participants immediately began a tai chi course and the other half (the control group) waited 8 weeks before beginning. at the end of 8 weeks, the individuals who had experienced tai chi had less arthritis pain that those who had not participated in the course.

Archeologists have discovered three sites showing conclusive evidence for the mastery of fire in tanzania, from a period slightly after the time that homo habilis was present in africa. these sites clearly were founded by homo erectus, the descendent species of homo habilis that migrated north, out of africa and into asia. homo erectus was known to have mastered fire, from ample evidence at sites in asia. there is no reason to attribute mastery of fire to homo ergaster, the descendent species of homo habilis that remained in africa.which of the following is an assumption on which the argument depends? (a) before their migration, homo erectus occupied african territory as far south as tanzania.(b) the strain of migration provided the selective pressure motivating homo erectus‘ mastery of fire.(c) homo ergaster would not have derived as much benefit from the mastery of fire as did homo erectus.(d) homo ergaster inherited all cultural knowledge from homo habilis, a species that did not have mastery of fire.(e) homo ergaster did not occupy regions as far south as tanzania until well after the time of these three sites.

Astudent from one of the research labs is having trouble preparing a slide for examination and photographing. the bacterial slide that he has brought to you was prepared using a commercially purchased stain. he has asked for your in determining what he is doing wrong so that he can change the lab protocols and continue on with his project. after examining the slide under oil immersion, you determine that no bacteria are present even though the student is able to show you the culture he used to make that slide that has visible growth in the liquid medium. which of the following statements does not explain the fact that there are no bacteria present on the student’s slide? by not allowing a glass slide to completely air dry before heat fixation, the flame will cause the surrounding water to boil and this will damage the bacterial cell. overheating during the fixation step boiled the water within the bacterial cells and resulted in the cells bursting. insufficient heating of the slide did not drive out the thin layer of water and this resulted in minimal bonding between the bacteria and the glass slide. rinsing with alcohol during the washing step stripped the bacteria off the glass slide. rinsing with alcohol during the washing step stripped the bacteria off the glass slide.